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Series 540 

Cartridge Tape Drive 

Product Specification 



QIC-02 Interface 



ciphi 




TABLE OF CONTENTS 



SECTION 1 - GENERAL DESCRIPTION 

INTRODUCTION 1 

Microprocessor Supervisory Control . 1 

Host Interface and Sequencer 1 

Write Logic and Sequencer 2 

Read Logic and Sequencer 2 

DataBuffer 2 

Basic Drive Interface 2 

SECTION 2 - QIC-02 INTERFACING 

INTRODUCTION 3 

ELECTRICAL INTERFACE 3 

DC Power Interface 3 

Interface Signal Levels 4 

Functional Interface 6 

540 INSTRUCTION SET 7 

QIC-02 Command Set 7 

Select Command (0000-NNNN) 8 

Select Drive/Lock Cartridge Command (0001-NNNN) 8 

Select Lock Command (1101-NNNN) 8 

Read Status Command (1100-0000) 13 

Read Extended Status Command (1110-0000) 16 

Write Data Command (0100-0000) 20 

Write Without Underruns Command (0100-0001) 22 

Write File Mark Command (0110-0000) . . 22 

Write N File Marks Command (0111-NNNN) 22 

WriteFilemarkOntheFly(62) 24 

Read Data Command (1000-0000) 24 

Read File Mark Command (1010-0000) 28 

Read On The Fly (82) 28 

Read N File Marks Command (1011-NNNN) 28 

Read Quarterback Format Command (0100-1001) 28 

Rewind Command (0010-0001) 33 

Erase Tape Command (0010-0010) 33 

Retension Command (0010-0100) 33 

Backspace (89) 33 

Seek End of Recorded Data Command (1010-0011) 33 

Block Search Command (AD) 33 

Run Self Test 1(C2) 35 

Run Self Test H(CA) 35 

SECTION 3 - ERROR PROCESSING & RECOVERY 

INTRODUCTION 41 

WRITE BUFFER UNDERRUN 43 

Read-After- Write Errors 43 

READ BUFFER UNDERRUN 44 



Read Data Errors 44 

Read Sequence Errors 45 

READ OR WRITE ABORT ERRORS 45 

NO DATA DETECTED ERRORS 45 

SECTION 4 - REPOSITION TIMING 

INTRODUCTION 47 

WRITE BUFFER CRITICAL TIMING 49 

Write Reposition 49 

JUMPER CONFIGURATION 50 



LIST OF FIGURES 



Figure 1. Host/Formatter Logical Interface 3 

Figure 2. Line Driver/Receiver Termination 4 

Figure 3. Read Status Timing Diagram 9 

Figure 4. Reset Timing Diagram 10 

Figure 5. Select Formatter Timing Diagram 11 

Figure 6. Select Lock Timing Diagram . . . . . 12 

Figure 7. Read Status Timing Diagram 13 

Figure 8. Read Extended Status Timing Diagram 17 

Figure 9. Write Data Timing Diagram 21 

Figure 10. Write File Mark Timing Diagram 23 

Figure 11. Write N File Marks Timing Diagram 25 

Figure 12. Write Filemark on the Fly (WFOTF) 26 

Figure 13. Read Data Timing Diagram 27 

Figure 14. Read Filemark Timing Diagram 29 

Figure 15. Read On The Fly (ROTF)(l of 2) . . . . 30 

Figure 15. Read On The Fly (ROTF) (2 of 2) 31 

Figure 16. Read N File Marks Timing Diagram 32 

Figure 17. BOT, Erase & Retension Timing Diagram 34 

Figure 18. Block Search Command 36 

Figure 19. Run Self Test I & II 37 

Figure 20. Write Buffer Underrun Events 47 

Figure 21. Write Buffer Underrun Flowchart 48 

Figure 22. Critical Write Timing Elements 49 

Figure 23. Reposition Timing Sequence 49 

LIST OF TABLES 

Table 1. Signal Levels 5 

Table 2. Input/Output Pin Assignments 5 

Table 3. Read Status Byte Summary 14 

Table 4. Read Extended Status III Format. 18 

Table 5. Exception Status Bytes 41 



m 



SECTION 1 
GENERAL DESCRIPTION 



INTRODUCnON 



The optional integral QIC-02 formatter supplied by Cipher for the 540 drive prov- 
ides the intelligence for tape formatting and QIC-02 interface control. The 
formatter board can be logically partitioned into 6 major functional blocks. They 
are: 

1) Microprocessor supervisory control 

2) Host interface and sequencer 

3) Write logic and sequencer 

4) Read logic and sequencer 

5) Data buffering 

6) Basic drive interface 

A general overview of the interrelationship of these 6 components is as follows. 

Microprocessor Supervisory Control 

At the heart of the QIC-02 formatter is the 8051 microprocessor and 8K of drive 
ROM (firmware). The 8051 is responsible for: 

1) Interpreting QIC-02 commands and responses 

2) Assigning one of four, 512-byte pages of data buffering to one of three 
sequencers (Host, Write, Read) 

3) Enabling the appropriate sequencer at the correct time 

4) Monitoring the sequencers for completion status 

5) Controlling tape motion and position 
Host Interface and Sequencer 

The host interface is composed of an 8-bit bi-directional bus that is used to 
transmit commands, status, and data to or from the host. In addition there are 
eight control lines that are used to facilitate communication between the host 
system and the Cipher QIC-02 tape drive. Their names and specific uses are 
covered in the "Interfacing" section of this manual module. The sequencer as- 
sociated with the host interface has the responsibility of transfering 512-byte data 
blocks to or from the host via the 8-bit bus to or from the microprocessor as- 
signed 512-byte page of buffering. 

1 



Write Logic and Sequencer 

The write logic under the control of its sequencer is responsible for: 

1) Sequencing 512-byte user data blocks from the assigned buffer page to 
the basic drive 

2) Dynamically performing a 4-bit to 5-bit GCR translation on the data, 
microprocessor supplied 4-byte block address and the 2 byte CRC field 
generated against the entire "logic block". 

Read Logic and Sequencer 

The read logic under the control of its sequencer is responsible for: 

1) Sequencing 512-byte user data blocks from the basic drive to the as- 
signed buffer page 

2) Dynamically performing a 5-bit to 4-bit translation on the data, four 
byte block address and 2 bytes of CRC. 

Data Buffer 

The data buffer is comprised of a 16384 by 1 RAM chip that is partitioned into 
four 4096-bit (512-byte) pages. Any page under 8051 control can be connected to 
any of the three sequencers. This feature provides for optimal buffer usage and 
assists in streaming. 

Basic Drive Interface 

The Basic Drive Interface is composed of latches that are utilized to communicate 
between the formatter board and basic drive board. 



SECTION 2 
QIC-02 INTERFACING 



INTRODUCTION 



Data commands and status are transferred to or from the 540 on an 8-bit bi- 
directional data bus, using asynchronous handshaking techniques to eliminate tight 
timing constraints. The interface is compatible with the standard QIC-02, Revision 
D. The logical interface between the host and the formatter in the 540 is il- 
lustrated in Figure 1. 



HOST 
SYSTEM 




ON LINE 


+- 


540 
FORMA'ITER 




REQUEST 


..._ — ^. 


^ 


READY 




EXCEPTION 


•^ 


n^runm; 


»- 




<z 


8-BIT DATA BUS 
XFER 


> 


ACK 




DIRC 






RESET 











Figure 1. Host/Formatter Logical Interface. 

ELECTRICAL INTERFACE 

The signals are connected through a 50-conductor edge connector. The mating 
connector is a 3M 3415-0001, or equivalent. The signal cable is a 50-conductor 
flat ribbon cable, such as the 3M 3365/50. The maximum cable length supported by 
the interface is 9.84 feet (3 meters). 

DC Power Interface 

The standard termination is 220 ohms to +5 VDC and 330 ohms to ground, or the 
Thevenin equivalent. The bi-directional data bus and the four control signals from 
the host are terminated at the drive. The bus and four control signals from the 
drive are terminated at the host. A typical driver/receiver termination configura- 
tion is illustrated in Figure 2. 



CPU 



TAPE DRIVE 



B> 



+5v 



220ft. 



O 



330«- 



+&f 



2200 




SIGNAL IN 



SIGNAL OUT- 



BIDIRECTIONAL BUS 



+5v 




<3 




Figure 2. Line Driver/Receiver Termination. 

Signals loaded by the drive, or the host, onto the interface are no more than 2.0 
mA, plus required terminations. 

Interface Signal Levels 

All s ignals to the host or to the drive use standard Transistor-Transistor Logic 
(TIL), as provided in Table 1. 

The odd numbered pins are connected to signal ground (gnd). The assignments for 
the even numbered pins are listed in Table 2. In the "To" column in this table, X 
means unused, B means bi-directional, D means drive, and H means host. 



Table 1. Signal Levels. 



Direction 


Logic 


0/1 


Voltage 
(VDQ 


Drive — >Host 


False 


0(high) 


2.4 - 5.25 




True 


l(low) 


- 0.55 


Host — > Drive 


False 


0(high) 


2.0 - 5.25 




True 


l(low) 


0-0.8 



Table 2. Input/Output Pin Assignments. 



Pin # Name To 



Description 



02 


N/U- 


X 


04 


N/U- 


X 


06 


N/U- 


X 


08 


N/U- 


X 


10 


HBP- 


B 


12 


HB7- 


B 


14 


HB6- 


B 


16 


HB5- 


B 


18 


HB4- 


B 


20 


HB3- 


B 


22 


HB2- 


B 


24 


HB1- 


B 


26 


HB0- 


B 


28 


ONL- 


D 



30 



REQ- 



D 



32 


RST- 


D 


34 


XFR- 


D 


36 


ACK- 


H 


38 


RDY- 


H 



Not Used (N/U) - unconnected signal line 



Host Bus odd parity - optional 
Host Bus bit 7 - MSB on 8-bit bus 
Host Bus bit 6 
Host Bus bit 5 
Host Bus bit 4 
Host Bus bit 3 
Host Bus bit 2 
Host Bus bit 1 

Host Bus bit -LSB on data bus 
On Line - Host activates signal before trans- 
ferring or terminating a Read or Write. 
Request - Host activates signal to indicate 
that, in Command mode, command data has 
been placed on the data bus. Also used in 
Status Input mode to indicate status has been 
taken from the bus. REQ- is used only when 
RDY or EXC is asserted by the drive. 
Reset - Initialize the drive and the EXC 
signal is asserted. 

Transfer - Host generates signal to indicate, in 
Write mode, that date has been placed on the 
data bus. In Read mode, it indicates that data 
has been taken from the bus. 
Acknowledge - Drive generates signal to indi- 
cate, in Write mode, data has been taken from 
the bus or, in Read mode, placed on the bus. 
Ready- Drive generates signal to indicate 
one of the following: 

1. - In Command Transfer mode, data has 



Table 2. Input/Output Pin Assignments continued. 



Pin # Name To 



Description 



40 



42 



EXC- 



DIR- 



H 



H 



44 


RES 


X 


46 


RES 


X 


48 


RES 


X 


50 


N/U- 


X 



been taken from the data bus or, in 
Status Input mode, data has been 
placed on the bus. 

O _ A T5fYT /^ortri/lfta J-n itioliTotmn /-vt» 

i-i. ~ ^ i. J~>V*r A, UUlUlUgV/ A.IX i.LXCLi.l^LLLl\_/lX, V71 

Erase command has been completed. 

3. - Drive is ready to receive the next 

block or, in Write mode, to receive 
a Write, Write File Mark, or Write 
N File Marks, from host. 

4. - In Write File Mark mode, a Write 

File Mark, or Write N Files Marks is 
completed. 

5. - Drive is ready to send next block 

or, in Read mode, receive a Read, 
Read N File Marks, or Read File 
Marks command from the host. 

6. - Drive is ready to receive a new 

command. 
Exception - Drive generates this signal when 
an exception condition exists in the drive. 
Host must issue a Status command or perform 
a Status input to determine the cause and 
clear the exception. 

Direction - Drive generates the signal that, 
when false, causes the host data bus drivers to 
assert their data bus levels and drive data bus 
drivers to assume a high impedance state. If 
true, the host assumes the high impedance 
state and the drive asserts its bus level. 
Reserved - Kept for test I/O. 



Not Used - Unconnected signal line. 



Functional Interface 

The interface signals ONL-, REQ-, and RST- can be easily generated by the host 
program, and output to the interface adapter register latches and drivers. Similar- 
ly, the drive formatter generated RDY- and EXC- should be input, through receiv- 
ers, to the host. 

Commands are transferred by simply loading each command into a register that is 
connected, through drivers, to the bi-directional data bus and implanting the 
required control signal protocol with the host program. Status input is similarly 
implemented by the host. In order to avoid prolonged waits by the host for the 
formatter to complete a command, the RDY- and EXC- lines are necessary. How- 
ever, the bi-directional bus control signal DIR- should only be used by the host 
interface adaptor to enable the host's bus drivers. 



540 INSTRUCTION SET 
QIC-02 Command Set 

The following is a summary of QIC-02 commands supported by the Cipher 540 tape 
drive. An in-depth description for each command and its associated timing can be 
found on the page listed with each command. 



OPCODE Command Name 


Page# 


Command 


(HEX) 






Type 




System Type Commands 






0M 


Formatter Select, LED off 


8 


S 


1M 


Formatter Select, LED on 


8 


O 


DM 


Formatter Select, Hold Position 


8 


V 


CO 


Read Status 


13 


S 


C4 


Read Extended Status 1 


16 


o 


E0 


Read Extended Status 3 

Write Type Commands 


16 


o 


40 


Write Data 


20 


s 


41 


Write Without Underrun 


22 


o 


60 


Write File Mark 


22 


s 


7M 


Write M File Marks 


22 


o 


62 


Write File Mark on the Fly 
Read Type Commands 


24 


V 


80 


Read Data 


24 


s 


A0 


Read File Mark 


28 


s 


82 


Read File Mark on the Fly 


28 


V 


BM 


Read M File Marks 


28 


o 


49 


Read QIC- 11 Format 

Position Type Commands 


28 


V 


21 


Rewind Tape 


33 


s 


22 


Erase Tape 


33 


s 


24 


Retension Tape 


33 


s 


89 


Backspace 1 Block 

Seek End of Recorded Data 


33 


o 


A3 


33 


o 


AD 


Locate Block N 


33 


V 


C2 


Run Self Test 


35 


o 


Note: 


M = Modifier Nibble Field 

S = Standard QIC-02 Command 

O = Optional QIC-02 Command 








V = Vendor Unique to Cipher Con 


imand 


1 



The host and 540 formatter communicate through the 8-bit bi-directional data bus. 
All transfers are asynchronous and eight bits wide. 

The Power On/Reset sequence provides the host with the device-oriented power-on 
procedure. It also provides a convenient method of initializing the drive during 
hardware or software debugging of the host's interface. 

When the power-on Reset times out or the RES- pulse terminates the operating 
parameters of the 540 initialize. The parameters default to the drive and the QIC- 
24 format for subsequent commands. Then, the drive becomes active, asserting 
EXC-, which makes the host issue a Read Status command. The drive responds 
with six status bytes, following the Request/Ready handshake illustrated in Figure 
3. Bit of byte 1 is set to indicate power-up or reset. 

Following the Reset, the physical drive recalibrates the Read/Write head positioner 
to Track 0, which causes a delay of approximately three seconds before the execu- 
tion of any motion command. Read/Write commands, following the reset, begin 
execution from BOT. Timing for the Reset sequence is illustrated in Figure 4. 

Select Command (0000-NNNN) 

This command allows the host to select one of up to four available drives, uniquely 
numbered from 1 to 4 as shown below. When the Select command is initiated, the 
formatter saves the tape drive address, selects the addressed drive, and alerts the 
host at the completion of the command sequence. A LED on the front panel of 
the selected 540 is illuminated during command execution. The drive remains 
selected until another Select command is initiated. Unit select jumpers W6 and W7 
are provided on the formatter. The timing diagram for the Select command is 
provided in Figure 5. 



NNNN 


W6 


W7 


Select 


0001 


In 


In 


Drive 


0010 


Out 


In 


Drive 1 


0100 


In 


Out 


Drive 2 


1000 


Out 


Out 


Drive 3 



Select Drive/Lock Cartridge Command (0001-NNNN) 

This optional command performs the functions of a Select command, except the 
LED is illuminated and remains on until a standard Select command is issued or the 
drive is reset. The timing for this command is the same as for a standard Select 
command. (See Figure 5.) 

Select Lock Command (1101-NNNN) 

This optional command is used with daisy chained formatted drives. It performs 
the functions of a Select command, except the tapes in both the selected and 
deselected drives are not rewound to BOT. Because these tapes stay at the cur- 
rent position, one 540 can copy from another 540 without rewinding to BOT or 
seeking the end-of-data position. The timing for this command is illustrated in 
Figure 6. 

8 



ONLINE h 




i > 



* > 



databus ^> <r\s^£^^T77X^ status bvtz xT777( (ZXE!S^!SfeZ^4ZZ 

XFER ) W \ h 



ACK h 



DIRCJ- 




RESETh 



Activity 

Tl-Host command to bus 
T2-Host sets REQUEST 
T3-Controller resets EXCEPTION 
T^-Controller sets READY 
T5-Hosts resets REQUEST 
T6-Bus data invalid 
T7-Controller resets READY 
T8-Controlier changes bus DIRC 
T9-First status byte to bus 
TiO-Controller sets READY 
Til-Host sets REQUEST 
T12-Controller resets READY 
Ti3-Bus data invalid 
T14-Host resets REQUEST 
T15-Last status byte to bus 
T16-Same asTIO 
T17-Same as Til 
T18-SameasT12 
T19-Sameas T13 
T20-SameasT14 
T21-Controller changes bus DIRC 
T22-Controller sets READY 
X -Don't Care 



^ * 







Criticai Timing 

N/A 

TUT2>0uS 

T>T*>10 uS 

T2*TO20 uS (500 uS nom.) 

T W5 > uS 

T4+T6>0uS 

20<T5+T7< 100 uS 

N/A 

N/A 

T7-T10>20 uS 

N/A 

Til-tfl2< 1 uS 

Tii+T13>0uS 

Tll*T14>20uS 

N/A 

Same as T10 

Same as T 1 1 

Same as T12 

Same as T13 

Same as T14 

N/A 

T20+T21 > uS 
T21+T22>0uS 



Figure 3. Read Status Timing Diagram. 
9 



UNLINfc 



REQUEST ^ 



////// ///J////////\ 




Activity 

Tl-Host asserts RESET 
T2-Controller disables ACK 
T3-Controller disables READY 
T^-Controller asserts EXCEPTION 
T5-Controller disables DIRC 
T6-Host disables RESET 



Critical Timing 

N/A 

T2<T6 + 100 NSec 
T1*T3<1 uS 
T1VT4<10 uS 
T1>T5 <10uS 
Tl+T6>25 uS 



NOTE: The drive may assert ACK when reset is asserted. 
X-Don't Care 



Figure 4. Reset Timing Diagram. 
10 



ONLINE h 



REQUEST \ 



READY 
EXCEPTION 




DATA BUS iT^C SELECT CQMMANP"^X/ /////////// \ 
XFER | 



ACK I- 



DIRC 



RESET h 



DRIVE SELECTED \ 



T9, V T10 

DRIVE A / \ DRIVE B 



Activity 

Tl-Host command to bus 
T2-Host sets REQUEST 
T3-Controller resets READY 
T4-Controller sets READY 
T5-Host resets REQUEST 
T6-Bus data invalid 
T7-Controller resets READY 
T8-Controller sets READY 
T9-Drive A Deselected 
TlO-Drive B Selected 

X-Don't Care 



Critical Timing 

N/A 

Tl+T2>0uS 

T2+T3< 1 uS 

T3+TO20 uS {500 uS nominal) 

T4+T5>0uS 

T4*T6>0uS 

20<T5*T7<100 uS 

T7VT8>20 uS 

T2VT9<170 uS 

T9*T10 >20 uS 



*If more than one drive is daisy chained, Drive A is the previously selected drive and 
Drive B is the drive addressed in the new Select command. 



Figure 5. Select Formatter Timing Diagram. 

11 



ONUNE H 



REQUEST \ 



READY \ 
EXCEPTION 




DATA BUS yTX SELECTCOMMAND X/ /////////// \ 
XFER | 



ACK h 



DIRC 



RESET 



DRIVE SELECTED 



T9 —-T10 
DRIVE A / \ DRIVE B 



Activity 

Tl-Host command to bus 
T2-Host sets REQUEST 
T3-Controller resets READY 
T4-Controller sets READY 
T5-Host resets REQUEST 
T6-Bus data invalid 
T7-Controlier resets READY 
T8-Controller sets READY 
T9-Drive A De-Selected 
TlO-Drive B Selected 

X-Don't care 



Critical Timing 

N/A 

TUT2>0uS 
T2-T3 < 1 uS 
50<T3VR< 500 uS 
Tf *T5 > uS 
T3VT6>0uS 
20<T5*T7<100 uS 
T7*T8>20 uS 
T2*T9< 170 uS 
T9VT10<20uS 



*If more than one formatted drive is daisy chained, Drive A is the previously selected 
drive, and Drive B is the drive addressed in the new Select command. 



Figure 6. Select Lock Timing Diagram. 
12 



Read Status Command (1100-0000) 

This command, originated by the host, provides the host with information about 
the selected drive. This information is transferred from the drive in the standard 
QIC-02 six status bytes. The timing diagram is provided in Figure 7. 



ONLINE h 



■* h- 




i ^ 



* > 



DATA BUS f> ^g|SS }5 ><7777^isT status wi* rnl\ \7 K L * S VvW» s yt///\//\// 
XFER ) H 1 h 



ACK h 



DIRC h 




RESETh 



Activity 

Tl-Host command to bus 
T2-Host sets REQUEST 
T3-Controller resets EXCEPTION 
T ^-Controller sets READY 
T5-Hosts resets REQUEST 
T6-Bus data invalid 
T7-Controller resets READY 
T8-Controller changes bus DIRC 
T9-First status byte to bus 
TlO-Controller sets READY 
T li-Host sets REQUEST 
T12-Controller resets READY 
T13-Bus data invalid 
T14-Host resets REQUEST 
T15-Last status byte to bus 
T16-Same as T10 
T17-Same as Til 
T18-SameasT12 
T19-Sameas T13 
T20-SameasT14 
T21-Controller changes bus DIRC 
T22-Controller sets READY 
X-Don't Care 



H * 




-\ I- 



/T2l" 



Critical Timing 

N/A 

TUT2>0uS 

T3VR>10 uS 

T2-»T4>20 uS (500 uS nom.) 

TWT5>0uS 

TW6>0uS 

20<T5->T7< 100 uS 

N/A 

N/A 

T7-T10>20 uS 

N/A 

T11-*T12< 1 uS 

Tll+T13>0uS 

Tll*Tl*>20uS 

N/A 

Same as T10 

Same as T 1 1 

Same as T12 

Same as T13 

Same as T14 

N/A 

T20+T21 > uS 
T21+T22>0uS 



Figure 7. Read Status Timing Diagram. 
13 



Table 3. Read Status Byte Summary. 



(MSB) 



(STO) Set, if any other bit in Byte is set. If Bit 
7 is set Exception may be set. 

(CNI) Cartridge Not In. Exception set if cartridge 
removed, and (1) drive selected by select drive 
with Lock Cartridge command; (2) motion 
command is issued; or (3) tape moved previous- 
ly from BOT. 

(DFF) Device Fault Flag. DFF sets Exception. Must 
be followed by a Read Status sequence to clear 
Exception. (Read Extended Status III contains 
information in Byte 25 to determine cause of 
fault.) DFF set when formatter detects 540 
condition which prohibits further command 
execution. For example: 

1. No tape motion (jammed cartridge) 

2. Failure to recognize or exit area between 
BOT/load point, or early warning/EOT. 

3. No tach pulses from capstan motor. 

4. Failure to complete command function in 
specified internal time. For example: not 
completing rewind once formatter initiates 
command. 

DFF indicates an unrecoverable 540 or cartridge 
error to user. 

(WRP) Write Protected cartridge. Set if cartridge 
write protect mechanism on safe. Remains set 
until cartridge is write enabled. Exception set 
if any Write or Erase command is issued when 
cartridge is write protected. 

(EOM) End of Media. Set when early warning hole 
detected on last track in write mode. Remains 
set while tape is at logical end of media. Not 
reset by Read Status. When set, Exception is 
set. 

(UDE) Unrecoverable Data Error. Set for unrecover- 
able data error during read or write operation. 
If set, Exception is set. Reset by Read Status. 

(BNL) Bad Block Not Located. Set to indicate drive 
not able to locate correct block on tape. If 
set, Exception is set. When set with (UDE), 
drive transfers filler data block or data from a 
different block to keep correct total block 
count. BNL reset by Read Status. 

14 



Table 3. Read Status Byte Summary continued. 



Byte No. Bit No. 



Definition 



(LSB) 



(FMD) File Mark Detected. Set when filemark 
block is read. Exception set and FMD reset by 
Read Status. 



1 (MSB) 7 
6 



(STI) Set,if any other bit in Byte 1 is set. If set, 
Exception may be set. 

(ILL) Illegal command. Exceptions and Bit 6 set 
under these conditions: 

1. On line not asserted when read or write 
type command attempted or in process. 

2. Non-implemented command is issued. 



3. 



4. 



Non-read type command issued without 
proper termination of write sequence. 

Non-write type command issued without 
proper termination of write sequence. ILL 
reset by Read Status. 



(NDT) No data detected. Set when drive determines 
no data is recorded on tape. If set, Exception 
is set. NDT reset by Read Status. 

(MBD) Marginal Block Detected. Set at detection of 
marginal data block. Enhanced track offset 
read recovery uses MBD to alert host if +4-mil 
or + 8-mil offset required to read recorded car- 
tridge. Exception set only if Exception and 
filemark read status are indicated. A set MBD 
indicates track position offset, when filemark 
was read. This status indicates to host a mar- 
ginally recorded cartridge. Host may deter- 
mine to write append tape, or recover data 
and rewrite cartridge. 

(BOM) Beginning of Medium. Bit set when drive is 
logically at BOT, Track 0. If set, Exception is 
set. Bit not reset by Read Status, but reset 
when tape moved away from logical BOT. 

(BPE) Bus Parity Error. Bit set when drive detects 
odd parity error on bus during data transfer to 
drive. If set, Exception is set. Odd parity is 
an odd number of active bits on bus. Parity 



15 



Table 3. Read Status Byte Summary continued. 



Byte No. Bit No. 


Definition 


1 


enabled by W8, W9, W10 jumper configuration 
on 540 formatter. Only data is checked for 
parity. 

(ERM) End of Recorded Media. Bit set when drive 
detects end of recorded media, or following a 
Seek End of Data command. If set, Exception 
is set. 


(LSB) 


(POR) Power On/Reset occurred set. Bit set follow- 
ing power on to drive or a reset from host. 
If set, Exception is set. Bit reset by a Read 
Status. 



Read Extended Status Command (1110-0000) 

This optional command, issued by the host, provides the host with information for 
fault isolation of the selected drive. This information is provided by the drive in 
64 bytes of vendor unique status data. The timing diagram for this command is 
provided in Figure 8. 



16 



online ^■ 



-» I- 




\ > 



DATA BUS f ^^^^><7777yiST status byte^TT^ fT X^VA™** / / A/ /]/ / 

. 1 >- 



XFER h 



ACK *■ 



DIRC h 




RESlTh 



Activity 

Tl-Host command to bus 
T2-Host sets REQUEST 
T3-Controller resets EXCEPTION 
T^-Controller sets READY 
T5-Hosts resets REQUEST 
T6-Bus data invalid 
T7-Controller resets READY 
T8-Controller changes bus DIRC 
T9-First status byte to bus 
TlO-Controller sets READY 
T 11-Host sets REQUEST 
T12-Controller resets READY 
T13-Bus data invalid 
T14-Host resets REQUEST 
T15-Last status byte to bus 
T16-Same as T10 
T17-Same as Til 
T18-SameasT12 
T19-SameasT13 
T20-SameasT14 
T21-Controller changes bus DIRC 
T22-Controller sets READY 
X-Don't Care 



H > 







Critical Timing 

N/A 

TUT2>0uS 

T3VT4>10 uS 

T2+T4>20 uS (500 uS nom.) 

TW5>0uS 

TW6>0uS 

20<T5+T7< 100 uS 

N/A 

N/A 

T7-T10>20 uS 

N/A 

Tll-tfl2< 1 uS 

TlUT13>0uS 

Tll*T14>20uS 

N/A 

Same as T10 

Same as Til 

Same as T12 

Same as T13 

Same as T14 

N/A 

T20+T21 > uS 
T21-»T22>0uS 



Figure 8. Read Extended Status Timing Diagram. 

17 



Table 4. Read Extended Status III Format. 



Byte (Hex) Byte & Bit Description 


00 (00) 


Basic Drive Control Register (bit map) 
7 - Reserved 




6 - Write Enable 




5 - Erase Enable 




4 - Reverse Enable 




3 - Go Enable 




2 - Reserved 


01 (01) 


Current Track/Lock Register 
7 thru 4 Bit On Current Track (MSB =7, LSB =4) 
3 thru Lock Bit Set By Host If(In) Select Cmd.Used 
2 thru Reserved 


02(02) 


Last Status (bit map) 
7 - CRC Error 




6 - Filemark 




5 - Gap Detected 
4-3 Reserved 




2 - Write Complete 
1 - Read Complete 
- Host Complete 


03 (03) 
thru 


Reserved 


12 (0C) 




13 (OD) 


Command Register 
7 thru - Reserved 


4(0E) 


Status Byte 


15 (OF) 


Status Byte 1 


16 (10) 


Status Byte 2, Data Error Counter 


17(11) 


Status Byte 3, Data Error Counter 


18 (12) 


Status Byte 4, Underrun Counter 


19 (13) 


Status Byte 5, Underrun Counter 


20 (14) 
thru 


Reserved 


23 (17) 




24 (18) 


Format Type (bit map) 
7-0 




6-0 



18 



Table 4. Read Extended Status continued. 

Byte (Hex) Byte & Bit Description 

5-0 
4-0 
3-0 
2-0 
1-X(0 = QIC-11) 

- X (3 = QIC-24) 

25 (19) Position Error Map for Device Fault Flag 

01 = CMD = Rev. + Go + Delay Error = Still at EOT 

02 = Drive in Zone With Go ON. Error = Unable to Reach 

EOT or BOT Within 1 Second 

03 = Error = No Tach. Pulses Motor Running less than 30IPS 

04 = CMD = Rev. + Go + Delay. Error = No BOT Within 1.5 

Minutes 

05 = Unable to Find Load Point or Early. Warning After Go 

From BOT or EOT + Timeout 

06 = Unable To Exit Zone Area After Go Issued + Delay 

07 = Speed Error 

08 = Speed Error At Zone 

09 = Acceleration Error 
OA = Speed 10 Percent 

OB =Speed Deviation 10 Percent 

OC =Motor Run Away 

OD =Main Board Is Busy Following Wait Timeout. Device 

Ready Line From Main To Formatter Board Did Not Go 

Ready 
OE 
OF 

10 Motor Not Moving When It Should Be 

11 Running 
12 

13 

14 = Fake Zone Indication False Early Warning or Load Point 
Detected 

17 = Consecutive Write Errors in Excess 

18 = Unable To Write The Target Block 

19 = Unable To Locate Elongated Gap For an Append 

26 (1A) 

thru Reserved 

29 (ID) 

30 (IE) Last Block Address (LSB) 

31 (IF) Last Block Address 

32 (20) Last Block Address 

33 (21) Last Block Address (MSB) 

34 (22) File Mark Count (usually set to 0) 

35 (23) 

19 



Table 4. Read Extended Status continued. 
Byte (Hex) Byte & Bit Description 

thru Reserved 

46 (2E) 

47 (2F) Offset Status 
48 130) Reserved 

49 (31) Append Up Count 

50 (32) Append Down Count 

51 (33) Reserved 

52 (34} Reserved 

53 (35) Number of Blocks Recovered at Current Position 

54 (36 ) Number os Blocks Recovered at Last Offset Position 

55 (37) Reserved 

56 (38) Reserved 

57 (39) Vendor I.D. Cipher = 01 

58 (3 A) Firmware Revision Level 

59 (3B) Select 

60 (3C) Previous Track Offset Bit Map 

61 (3D) Previous Track Offset Bit Map 

62 (3E) Previous Track Offset Bit Map 

63 (3F) Previous Track Offset Bit Map 



Write Data Command (0100-0000) 

The Write command can only be issued by the host after ONL- is asserted. When 
the drive is ready for a data block transfer, the RDY- line is activated. However, 
if the host asserts a XFER- between blocks before RDY- has been asserted, the 
Ready line may not be asserted. 

When Ready has been asserted to indicate a data block boundary, the host can 
terminate the Write command by issuing a Write File Mark or Write N File Mark 
command. Either command will stop tape motion and the drive will maintain the 
present tape position until another command is issued. When RDY- is active, the 
host can terminate the Write command by de-activating ONL-. This action will 
write a file mark and rewind the tape to BOT. 

If the Write command is issued after the insertion of a cartridge, or a RST-pulse, 
writing starts at BOT. Otherwise, writing begins at the current tape position. 

If the drive unsuccessfully attempts to write a data block 16 times, the Write- 
command is terminated, EXC- is set, and the tape is rewound. 

When the drive detects the Early Warning hole on the last track, the drive stops 
accepting data blocks from the host, terminates the Write command, and uses an 
EXC- and Read status sequence to report an End-Of-Media condition. Then, if 
another Write command is issued, a final data transfer of 1,024 bytes can be made. 
A timing diagram for the Write command is provided in Figure 9. 

20 



T38 




EXCEPTION t- 






REAOY FOR 
JND SLOCK 



DATA BUS ^C 
tfFEl? I 



— v **D ■LOCK/ -- — 

23K— <n™ 



-* » 



H * 



DTKc" h 



fiESET i- 



N> 



T26 



T19* 



-« I- 



t— >• 








>-t 

CD 








VO 








3 


Activity 


Critical Timing 




Tl-Host command to bus 


N/A 




r-t- 

CD 


T2-Host sets ONLINE 


N/A 




r-t- 

H 


T3-Host sets REQUEST 


T2VT3 > uS 




T ^-Controller resets READY 


T3*T»< 1 uS 




T5~Controller sets READY 


TfVT5> 20 uS (500 uS nominal) 


T6-Host resets REQUEST 


T5-*T6 >0uS 




T7-Bus data invalid 


T5-»T7> OuS 




B 


T8-Controller resets READY 


20<T6VT8<100uS 






T9-Controller sets READY 


T8-»T9>20 uS 




CfQ 


TlO-Host data to bus 


N/A 




a 


TU-Host sets XFER 


Tl(Wll>-«)nS* 




T12-Controller resets READY 


T1UT12 1 uS 




T13-Controller sets ACK 


0.5<T11VT13< 100 uS 






Tl<f-Host rests XFER 


T1UT14 >0uS 




P 


T15-Bus data invalid 


T13*T15 >0uS 




T16-Formatter resets ACK 


0<T14-T16< 3uS 






T 17- Host data to bus 


N/A 






T18-Same as Til* 


Same as Til 






T19-SameasT13 


Same as T13 






T20-Same as Tl^ 


Same as T14 






J=^sT40. 



1ST DATA BVfTV ) f~ y LAST BLOCK ~X7 7 



T30 



T33^ ^T 



T36 



-i »- 



Activity 

T21-Same as T15 
T22-Same asT16 
T23-Controller sets READY 
T24-Host data to bus 
T25-Host sets XFER 
T26-Controller resets READY 
T27-Controller sets ACK 
T28-Host resets XFER 
T29-Bus data invalid 
T30-Controller resets ACK 
T31-Host data to bus 
T32-Host sets XFER 
T33-Controller sets ACK 
T34-Host resets XFER 
T35-Bus data invalid 
T36-Controller resets ACK 
T37-Controller sets READY 
T38-Host resets ONLINE 
T39-Controller resets READY 
TW-Controller set READY 



FORMATTER 

AUTOMATICALLY . 

S85WT lUlllllllin 



-i REWINDS TO BOT t 

(MECHANICAL 
H DELAY) 



Critical Timing 



Same 


asT15 


Same 


asT16 


T22->T23>100uS 


N/A 




Same as T 1 1* 


Same 


asT12 


Same as T13 


Same 


asT14 


Same 


asT15 


Same 


asT16 


N/A 




Same 


asT18 


Same as T19 


Same 


asT20 


N/A 




Same 


asT22 


Same 


asT23 


N/A 




N/A 




N/A 





* T 1 1 may precede T 10 by up to '+0 nS 



Write Mode Option 

An optional bus parity check can be enabled by installing jumper W6 on the for- 
matter pcb with this option: 

o Data bytes, not commands, are checked for parity. 

r\ T Tt-» +i-w CH vkn^^r-^^^^A^ „-« ~11~...~ A u_j vrrr» i nnn . . _t j 

\j ^j^j v\j u\j uaiiuBctuiiua aic anuwcu uciwccn yvris.- emu nor- VilllU. 

o EXC- is set to parity error detected, and a data block with a parity 
error is not written to tape. 

o Valid data buffers are written to tape and the buffer in error is cleared. 

o Recovery from a parity error is accomplished by the host reading status, 
then issuing another Write command. If this is not done,it causes a re- 
wind abort with illegal command status. 

Write Without Undemms Command (0100-0001) 

This optional command keeps the tape running when there is no data available in 
the Write mode. This is accomplished by writing an elongated preamble and/or 
redundant blocks until data becomes available or the end of the tape is reached. 
The timing for this command is the same as for a standard Write command. (See 
Figure 9). 

The Write Without Underrun Function (repetitively writing the last transferred 
block) may be terminated by the host system in one of three ways. They are: 

o Issue next data block 

o Issue write filemark type command 

o Taking On Line signal false 

If the host system supplies the "next" data block (N + 1) the formatter will repeti- 
tively write N + 1 until the host supplies N + 2 etc. Severe host underruns after 
issuing WWU command will impact overall capacity. The formatter itself will 
"time out" the WWU command whenever it encounters the physical end of the 
track. 

Write File Mark Command (0110-0000) 

This command writes a file mark on the tape in the selected drive. A Write File 
Mark (WFM) command, following a cartridge insertion or RST- pulsed, writes the 
mark at the BOT. Otherwise, the mark is written at the current tape position. 
The timing diagram for the WFM command is illustrated in Figure 10. 

Write N File Marks Command (0111-NNNN) 

This optional command is identical to the WFM, except the number of file marks 
to be written is specified by the binary value of NNNN. If NNNN is made equal to 

22 



ONLINE t 




RESET Y 



START 

TAPE 

MOTION 



FORMATTER 

WRITES f 

INTERNALLY 
GENERATED FILE 



■1 



h- 




T11 

START > 
i TAPE f 
REWIND 



.T12 



_ R 'T!. F '. LE ._ ^ / / / A °MARK ON TAPE = (///// /I 

\ » 



STOP 

TAPE 

MOTION 



■* 



y/nn \ 



Activity 

Tl-Host command to bus 
T2-Host sets ONLINE 
T3-Host sets REQUEST 
T4-Controiler resets READY 
T5-Controiler sets READY 
T6-Host resets REQUEST 
T7-Bus data invalid 
T8-Controller resets READY 
T9-Controller sets READY 
TlO-Host resets ONLINE 
Til-Controller resets READY 
T12-Controller sets READY (at BOT) 



Critical Timing 

N/A 

Tl-*T2>0uS 

T2-T3>0us 

T3-»T4<1 uS 

T W5 > 20 uS (500 uS nominal) 

T5-*T6>0uS 

T>T7>0uS 

T20<T6->T8<100uS 

N/A 

T9+Ti0>0uS 

N/A 

N/A 



Figure 10. Write File Mark Timing Diagram. 

23 



0, the operation is not performed. The timing diagram for this command is il- 
lustrated in Figure 11. 

Write Filemark On the Fly (62) 

The WFOTF command has all the attributes of a Write Filemark command, except 
tape motion is not terminated immediately after writing the filemark. Instead, the 

^ACi wrifrpc an AlnncrQtArl nnctamKlA \i/oitinrr fr\r tVi/a Vir*ct +r\ rocnnnH xintVi o na\ir 

w iv "Aiwu **" v^w J-J-f^vAVW V« WVUlUlUUAVj TTU11.111L 1WI LrA-AW UV/iJk \,\J IWOpV^liU Willi Ct 11WW 

Write command. If the host fails to respond with a new Write command within 7.0 
msec, the 540 terminates the Write command and stops tape motion. If the host 
reinstructs the 540 with a new Write command within the allowed 7.0 msec, then 
an additional 3.5 msec, is allowed to complete the data block transfer from the 
host to the 540. If the 540 is reinstructed within the 7.0 msec, but a 512 byte 
data block is not transferred within the 10.5 msec, time allowed, the 540 will per- 
form a write underrun sequence and stop tape motion. If the data block transfer 
is completed after the underrun, the 540 will reposition and continue writing as if 
following a normal underrun. 

Proper termination of a Write command can be accomplished in one of two ways. 
First, after issuing a WFTOFF, the host can force a write underrun condition. In 
this case, tape motion is terminated and the 540 exits the write mode. Second, 
the host can inactivate On-line. In this case, a file mark is written and the tape 
is rewound. (Timing for WFOTF is shown in Figure 12.) 

Read Data Command (1000-0000) 

The Read command can only be issued by the host after an ONL- is asserted. 
When the drive is ready for a data block transfer, the RDY-line is asserted. How- 
ever if the host begins transferring between blocks by asserting ACK-before RDY- 
is asserted, the RDY line may not be asserted. 

When a file mark is read, the Read command is terminated by the drive. This ac- 
tion stops the tape, and asserts EXC-. Then, the host must issue a Read Status 
command to clear the exception. 

The Read command can also be terminated by issuing a Read File mark or Read N 
File Mark command when RDY- is asserted. With either of these commands, the 
drive reads to the designated file mark, sets EXZC- and stops tape motion. 

The Read command can be terminated by de-activating ONL-, when Ready has been 
asserted. This sequence rewinds the tape to BOT. 

If the drive is unable to read a data block after 16 attempts, EXC- is asserted and 
the drive stops at the present tape position. 

A Read command following a cartridge insertion, or RST-pulse, starts at BOT. 
Otherwise, the Read starts at the current tape position. The timing diagram for 
the Read command is illustrated in Figure 13. 



24 




EXCEPTION 
DATA 3US 

tela 

ACK 

owe 
reset 



/T1 T7 4) 



START 

TAPS 

MOTION 



CONTROUEB 

WRITES 
tNTEHNAUr 



t- 



T11 



*-v ^^"1 START 
1 V * »TAPS > 



T12 



REWINO 



S Z7777777S G K?r2if 2ZZZZZZZZZJ 
— j s 



STCP 
TAPS 
MOTION 



■4 



y/////////\ 



Activity 

Tl-Host command to bus 
T2-Host sets ONLINE 
T3-Host sets REQUEST 
T4-ControUer resets READY 
T5-Controller sets READY 
T6-Host resets REQUEST 
T7-Bus data invalid 
T8-Controller resets READY 
T9-Controller sets READY 
TlO-Host resets ONLINE 
Til-Controller resets READY 
T12-Controller sets READY (at BOT) 



Critical Timing 

N/A 

TUT2>0uS 

T2VT3> OuS 

T3VR< 1 uS 

TW5>20 uS (500 uS nom.) 

T5+T6>0uS 

T5*T7 > uS 

20<T6-»T8< 100-uS 

N/A 

T9-»T10>0uS 

N/A 

N/A 



Figure 11. Write N File Marks Timing Diagram. 

25 



ONLINE 
REQUEST 

READY 

EXCEPTION " =C 

17 < 

DATA BUS %^ QWTM0TP Comnand *^W////////sfa 

XFER ■ -^ 

ACK 

DIRC 

RESET 

540 wr i tes 
an interna 1 ly 
generated file 
mark 



If no new 
comnand is 
issued, tape 




the Wr i te 
comand is 
terminated 



Tape motio'n 
cent inues 

Ready for 
next write 
type command 





Write File mark 


on the Fly 






ACTIVITY 


TIMING 




Ti 


Host sets ONLINE 


N/A 




T2 


Host command to bus 


T1-*T2 >0uS 




T3 


Host sets REQUEST 


T2-*T3>0uS 




Ik 


Controller resets READY 


T3—T4<1 uS 




15 


Controller sets READY 


T4-T5 >20 uS {500 uS nom.) 


T6 


Host resets REQUEST 


T5^T6>0uS 




17 


Bus data invalid 


T5— T7>0uS 




T8 


Controller resets READY 


20 uS<T6-T8<100uS 




T9 


Controller sets READY 


N/A 




T10 


No command issued 


T9-T10>7 mS 





Write terminated 



Figure 12. Write Fileraark on the Fly (WFOTF). 

26 



to 



£1 



a> 
a. 

a 

r-t- 

H 



crq 

a 

Co 
OQ 

>-t 
CO 

B 




-I H 



1ST BLOCK 
START f-jjQ^READY, 



T8 TAPE 
1 MOTION/ 



DATA BUS % K READ COMMAND 
XFER » 



ACK f- 



OIRC h- 



RESET h 



^xZZjREAD 
" *1ST 



Til i 



H »- 



T24 



??K 



T28. 



"* 



T39 




Activity 

Tl-Host command to bus 
T2-Host sets ONLINE 
T3-Host sets REQUEST 
T4-Controller resets READY 
T5-Controller sets READY 
T6-Host resets REQUEST 
T7-Bus data invalid 
T8-Controller resets READY 
T9-Controller changes DIRC 
TlO-First data byte to bus 
Til-Controller sets READY 
T12-Contr oiler sets ACK 
T13-Host sets XFER 
T14-Controller resets READY 
T15-Formatter resets ACK 
T16-Host data to bus 
T17-Host resets XFER 
T18-Busdata valid 
T19-Formatter sets ACK 
T20-Host sets XFER 



P CDATA BYTE *7777? f7 >!ST BYTE NE>»f777] 

. j l Tia niZ~^ t ,] T BLOC . K 1^ ™9 - 



LAST BYTE ___ 
(LAST BLOCK>C / /i > ^'t-E MARfeff'// yj 



TAPE 

MOTION 
* STOPS 



-* I- 



Critical Timing 

N/A 

N/A 

T2-T3> OuS 

T3*T«< 1 uS 

T«^T5> 20 uS (500 uS nominal) 

T5-T6> uS 

T5VT7> OuS 

20<T6-T8<100 uS 

N/A 

N/A 

N/A 

T1UT12>- fOnS* 

T12-»T13> OuS 

T13VT14< 1 uS 

0.5<T13-T15<3uS 

T13*T16>0uS 

T15^T17>0uS 

N/A 

Same as T12* 

Same as T13 




CPU 



Activity Cri tical Timing 

T21-Controller resets ACK Same as T15 

T22-Bus data invalid Same as T16 

T23-Host resets XFER Same as T17 

T24-Controller sets READY N/A 

T25-First byte to bus N/A 

T26-Controller sets ACK Same as T12* 

T27-Host sets XFER SameasT13 

T28-Controller resets XFER Same as T14 

T29-Controller resets ACK Same as T15 

T30-Bus data invalid Same as T16 

T31-Host resets XFER Same as T17 

T32-Last byte to bus N/A 

T33-Controller sets ACK Same as T12* 

T34-Host sets XFER Same as T13 

T35-Controller resets ACK Same as T 15 

T36-Bus data invalid Same as T16 

T37-Host resets XFER Same as T17 
T38-Controller sets EXCEPTION N/A 

T39-Change bus direction N/A 



4 SENDS 
READ 
STATUS 
COMMAND 



* T 12 may precede T 11 by up to 40 nS 



Read Mode Option 

A Parity option enables the bus parity generator by installing jumper W6 on the 
formatter pcb. With this option: 

o The 540 generates the parity bit with 50 nanoseconds maximum delav 

uum nv^tv- iu M.XXJL - vauu, 

o The 540 accepts a backspace command while in a Read sequence to reco- 
ver from a Read parity error. Any other command will cause a rewind 
abort with illegal command status. 

Read File Mark Command (1010-0000) 

This command moves the tape on the selected drive to the next file mark. A Read 
File Mark (RFM) command, following a cartridge insertion or RST- pulse, starts 
reading at the BOT. Otherwise, reading starts at the current tape position. The 
timing diagram for the RFM command is illustrated in Figure 14. 

Read On The Fly (82) 

The ROTF command has all the attributes of a Read command, except tape motion 
is not terminated immediately after reading the file mark. This allows the host to 
maintain streaming, when reading cartridges written with a large number of short 
files. 

When the host issues a ROTF command, the 540 starts reading. If a filemark is 
detected, the 540 will set an Exception. To maintain streaming, the host must 
issue a read Status command, complete a read status sequence, and reinstruct the 
540 with a new ROTF command within 8 msec. If the host is unable to meet 
these requirements, a read overrun will occur, tape motion will be stopped, and the 
read will be terminated. (Timing for ROTF is shown if Figure 15.) 



Read N File Marks Command (1011-NNNN) 

This optional command is identical to the RFM, except the number of file marks to 
be read is specified by the binary value of NNNN. If NNNN is made equal to 0, 
the operation is not performed, the timing diagram for this command is illustrated 
in Figure 16. 

Read Quarterback Format Command (0100-1001) 

This vendor-unique command changes the 540 parameter logic to read the format of 
the Cipher Quarterback 771 * 4-track tape. All 540 commands, except the Write opera- 
tions, may be used in this mode. A Power-On or RST-pulse restores the drive to 
the QIC-24 configuration. 



28 




START TAPE MOTION 



READ DATA BLOCKS 

UNTIL FILE MARK 

BLOCK FOUND 



T9^ 



ytZnX STOP TAPE MOTION (///////// 



ACK Y 



DlRC" 



RTSET Y 



Activity 

Tl-Host command to bus 
T2-Host sets ONLINE 
T3-Host sets REQUEST 
T4-ControUer resets READY 
T5-Controller sets READY 
T6-Host resets REQUEST 
T7-Bus data invalid 
T8-Controller resets READY 
T9-Controller sets EXCEPTION 



Critical Timing 

N/A 

Tl*T2>0uS 

T2+T3>QuS 

T3+R< 1 uS 

TW5>20 uS (500 uS nominal) 

T5+T6>0uS 

TM7>0uS 

20<T6-*T8< 100 uS 

N/A 



* System must issue READ STATUS command 



Figure 14. Read Filemark Timing Diagram. 



ONLINE 
REQUEST 

READY 
EXCEPTION 



"\T2. 



xi_/^ — 



■\njL^/fHT 



-r 
-r 



jl 



37^ 



110 



T16 



DATA BUS V//////////SX T-%^?f^/ZZ/ZZ^ 
XFER 



ACK 

dTrc 

RESET 



NLli-Xi 



117 



vT12 



yTTT 



-^. TO 



-f 

-r 



ONLINE 

REQUES T 

READY 



Y 



AJ 



127 



Sl30 



EXCEPT ION y 



\ T29 X rT 



>Gi 



-Xb<P 
_/T37 



DATA BUS 



T18 



T22 



T25 



XT28 



T31 T3f 



T38 



XFER 



ACK 

DIRC 
RESET 



M2th^yte>2Z^Cf'^ Mark X^XXXX/Z/M ^Read Status S^^^>^tQ^^T^J 

\ T2 ° /T2l 

>Hl_yF2l — 



-r 



./t? 



"^\T33_ 



Tl CPU command to bus 

T2 CPU sets ONLINE 

T3 CPU set REQUEST 

Tt Formatter resets READY 

T5 Formatter sets READY 

T6 CPU resets REQUEST 

T7 Bus data invalid 

T8 Formatter resets READY 

T9 Formatter changes DIRC 

TIO Data byte to bus 

Tl 1 Formatter sets READY 

T12 Formatter sets ACK 

TI3 CPU sets XFER 

Tl<f Formatter resets READY 

T15 Formatter reset ACK 

T16 Bus data invalid 

T17 CPU resets XFER 

T18 Data to bus 

T19 Formatter sets ACK 

T20 CPU sets XFER 

T21 Formatter resets ACK 

T22 Bus data invalid 

T23 CPU resets XFER 

T2*» Changes bus DIRC 

T25 Formatter sets exception 

T26 CPU command to bus 

T27 CPU sets REQUEST 

T28 Formatter resets exception 

T29 Formatter sets READY 

T30 CPU resets REQUEST 

T31 Bus data invalid 

T32 Formatter resets READY 

T33 Formatter changes bus DIRC 

T3*f First status byte to bus 

T35 Formatter sets ready 

T36 CPU sets REQUEST 

T37 Formatter resets READY 

T38 Bus data invalid 

T39 CPU resets REQUEST 



N/A 

N/A 

T2-T3>0 uS 

T3-PK 1 uS 

T4~T5>20 uS (500 uS nom.) 

T5-T6>0 uS 

T5-T7>0 uS 

20 uS<T6-T8<100 uS 

N/A 

N/A 

N/A 

Tll-.T12>-40nS 

T12-TlI3>0uS 

T13-TI«< 1 uS 
0.5uS<T13-T15<3uS 

T13-.T16>j)uS 
T15-T17>0uS 

N/A 

T18-.TI9>0uS 

T19-T2O>0uS 

0.5uS<T20-T2K3uS 

T20-T22 0uS 

T21-T23 0uS 

T23-.T24 0uS 

T2fc-.T25 uS 

N/A 

T26-T27>0 uS 

T27-T28>0 uS 

T27-T29>20 uS (500 uS nom. 

T29-T3O>0 uS 

T29-T31>0uS 

20 uS<T30-T32<100uS 

N/A 

N/A 

T32-»T35>20 uS 

N/A 

T36-J37<2 uS 

T36-T38>0 uS 

T36-T39>20 uS 



Figure 15. Read On The Fly (ROTF)(l of 2). 

30 



ONLINE 



£■ 



EQUEST f 



^EADY 



CEPTIONf. 



— \J^£ 



/t£7 



>J*! 



j^xyi 



r 



X*j 



yrio^Nj^ /w \ T57 / T60 *" 



T*0 



T** 



T*8 



T53 



T56 



T62 



DATA BUS ^^^^j^^<g22^ ^^^^^^^^ ^T^ d F?^ >g^^^ C "t Byte ^ ^ 
XFER f SJ59 /T63-^" 



ACK 

DIRC 
RESET 



f- 



V** / T6T 



f- 



./T46" 



N£ 



-f 



f- 



ONLINE 

REQUEST 

READY 



£ 



-f 



EXCEPT I ONf- 



T6* 



T68 



NZ: 



T72 



£ 



data bus Z x&^*^///////// /£ fiu Ma rk y 77 7///////////M 

XFER f \T66 y f^9 f 

? ST«* /?67 



ACK 

DlRC 
RESET 



f" 



yrfo 



f 



■f 





ACTIVITY 


TIMING 


T*0 


Last status byte to bus 


N/A 


Tfl 


Formatter sets READY 


Same as 735 


T*2 


CPU sets request 


Same as T36 


7*3 


Formatter resets READY 


Same as T37 


TW 


Bus data invalid 


Same as 738 


7*5 


CPU resets REQUEST 


Same as T39 


7*6 


Formatter changes bus DIRC 


T*5-T*6> uS 


Vi7 


Formatter sets READY 


T*6-T*7> I uS 


T*8 


CPU command to bus 


N/A 


T*9 


CPU sets REQUEST 


N/A 


T50 


Formatter resets READY 


T*9-»T50< 1 uS 


T51 


Formatter sets READY 


T50- T51 >20 uS (500 uS nom.) 


752 


CPU resets REQUEST 


T25-T52<8 mS 


T53 


Bus data invalid 


T51-T53 0uS 


75* 


Formatter resets READY 


20uS<T52-T5*<200uS 


755 


Formatter changes DIRC 


N/A 


756 


Data byte to bus 


N/A 


757 


Formatter sets READY 


N/A 


758 


Formatter sets ACK 


757-758>-*0nS 


759 


CPU sets XFER 


758~759>0uS 


T60 


Formatter resets READY 


759-760<l uS 


T61 


Formatter resets ACK 


0.5 uS<759-.76i<3 uS 


762 


Bus data invalid 


759-762>0 uS 


T63 


CPU resets XFER 


761-763>0uS 


76* 


Data to bus 


N/A 


T65 


Formatter sets ACK 


76*-J65>0 uS 


T66 


CPU sets XFER 


765-J66>0 uS 


767 


Formatter resets ACK 


0.5 uS<766-767<3 uS 


T68 


Bus data invalid 


766-768 >0uS 


T69 


CPU resets XFER 


767-769>0 uS 


T70 


Changes bus DIRC 


769-770 >0 uS 


T71 


Formatter sets exception 


770-771 >0uS 


T72 


Read terminated 


771 -772 >8 mS 



Figure 15. Read On The Fly (ROTF)(2 of 2). 



31 



ONLINE ' 



T5 



REQUEST 

REAOY 

EXCEPTION 

OATA 8US 

XFEfl 



OlflC 



RESET 



VT3 

c 



st*& 



Ezx 



T1 




Ta : READ OATA BLOCXS 
- » UNTIL RLE MARK 
BLOCX FOUND 






XZZZ2Z} 



STOP TAPE MOTION 



ACX 



fr 



STAflT TA PS MOT ION J- 
H 



t3^ 



j 1 

s 1 



Activity 

Tl-Host command to bus 
T2-Host sets ONLINE 
T3-Host sets REQUEST 
T^-Controller resets READY 
T5-Controller sets READY 
T6-Host resets REQUEST 
T7-Bus data invalid 
T8-Controller resets READY 
T9-Controller sets EXCEPTION 

*System must issue READ STATUS command 



Critical Timing 

N/A 

TM*2>0uS 

T2VT3>0uS 

T3+TK 1 uS 

T4-»T5>20 uS (500 uS nom.) 

T5+T6>0uS 

T4+T7 > uS 

20<T6-»T8< 100 uS 

N/A 



Figure 16. Read N File Marks Timing Diagram. 

32 



Rewind Command (0010-0001) 

This command positions the tape in the selected drive to the Beginning Of Tape 
(BOT). The timing diagram for this command is illustrated in Figure 17. 

Erase Tape Command (0010-0010) 

This command erases all the tape tracks from BOT to EOT, then deactivates the 
Erase bar and returns to BOT. This command fulfills the requirements of in- 
itialization. Timing for Erase Tape is the same as for the BOT command. (See 
Figure 17) 

Retension Command (0010-0100) 

This Command retensions the tape by returning to BOT; going from BOT to EOT; 
then returning to BOT. This command also fulfills the requirements of initializa- 
tion. Timing For Retension is the same as for the BOT command. (See Figure 17) 

Backspace (89) 

When nested in a read sequence, it is actually a Backspace Read which physically 
repositions and rereads the previous data block. Once the data block is read, the 
command returns the tape to the original position. If the data block is not read 
by the host, multiple nested backspaces will position tape reverse a block at a time. 

The 540 presents the first data byte of the previous data block command to the 
bus, and maintains the read sequence. This is a particularly useful way to recover 
from a read parity error. The read sequence is terminated if a filemark is read, 
and the 540 must be reinstructed with a new Read command to continue reading. 

The Backspace command can also be a stand-alone instruction. In this case, it 
positions the tape, but does not present data to the bus. Multiple commands will 
position tape reverse a block at a time. 

A Backspace command issued at BOT results in an Exception. 

Seek End of Recorded Data Command (1010-0011) 

This optional command instructs the drive to find the end of the recorded data. 
Once found, new data may be appended by another Write command. The timing for 
this command is essentially the same as for a Read File Mark command. (See Figure 
14.) No data is transferred, and the completion of the command is indicated by an 
Exception signal and the End of Recorded Media status bit. 

Block Search Command (AD) 

This command allows the host to search for a specific block on tape without stream- 
ing sequentially through the entire tape. The sequence for this command is: 

1. The host issues the Block Search command followed by a 4-byte block, 

33 




COMMAND X\\"V 



TAPE 
MOTION 



^vIL 



KWVWWWl 



ACK h 



OIRC h 



RESET H 



Activity 

Tl-Host command to bus 
T2-Host sets REQUEST 
T3-Controller resets READY 
T^-Controller sets READY 
T5-Host resets REQUEST 
T6-Bus data invalid 
T7-Controller resets READY 
T8-Controller sets READY 

X-Don't Care 



Critical Timing 

N/A 

Tl-»T2>0uS 

T2+T3 < 1 uS 

T3+T4 >20 uS (500 uS nominal) 

T4-*T5 > uS 

T*^T6 > uS 

20<T5-»T7< 100 uS 

T7*T8>20 uS 



Figure 17. BOT, Erase & Retension Timing Diagram. 

34 



using the request/ready handshake. The most significant block address 
byte is issued first. 

2. The 540 calculates a track position and determines motor direction. 

3. The 540 enables the capstan motor, and updates the track position. 

4. The 540 searches for the target block, minus one. 

5. When found, the 540 enables Ready. 

6. If the block search was nested in a Read command, the host may resume 
reading. If not, tape motion stops,the 540 terminates the search and 
waits for another command. 

7. If the 540 fails to locate the target block, it will reposition and try 
again. If the 540 again fails to locate the target block, the tape is rewo- 
und, Exception is set, and the command aborted. Following an abort, 
the following read status will show in Status Bytes and ^indicating an 
unrecoverable data error and BOT: 

Byte Byte 1 

100X0100 10001000 



Before using the Search command, it is necessary to know how many data blocks 
are recorded on a cartridge. Tape block addresses are sequential and the first 
block address convenient method of identifying block addresses is to write a label 
block in the data field as either the first or last block in a file. This block can 
then be used as a reference, prior to using the Search command. (Timing for Block 
Search command is shown in Figure 18.) 

Run Self Test 1 (C2) 

The command performs a check sum test. Following completion, a Read Status 
Command should be issued to verify results in Status Byte 3, as shown below. 
Command timing is illustrated in Figure 19. 

Status Byte 3: 

00 = Self Test not performed 

11 = Self Test Complete. No error. 

24 = Self Test failed. Check sum error. 



Run Self Test H(CA) 

This command performs the following sequential tests and reports status in Bytes 
3, 4 and 5. After each test has passed, the next test is automatically run. Follow- 
ing completion, a Read Status Command should be issued to verify results. Command 
timing is illustrated in Figure 19. 

35 




T10 



T15 



T34 



T39 



ONLINE 
REQUEST 

READY 
EXCEPTION 

T2 77 HU 112 118 T23 1 /& 131 i->*» i.>* -\ / 

DATA BUS ^Gi^nd 5 !!^ £ZZ 

XFER ' * 

ACK 

DlRC 
RESET 



<£ 



l-t 
CT> 






po 






dd 






o 
o 




ACTIVITY 


OJ 00 


Tl 


Host sets ONLINE 


0"\ CD 
P 


T2 


Host command to bus 


o 

tr 


T3 


Host sets REQUEST 
Controller resets READY 


o 


15 


Controller sets READY 


o 


T6 
T7 


Host resets REQUEST 
Bus data invalid 


p 


T8 


Controller resets READY 


p 


T9 


Controller sets READY 


T10 
Til 
T12 


Bus data valid byte (MSB) 
Host sets REQUEST 
Controller resets READY 




T13 


Controller sets READY 




Tl* 
T15 


Host resets REQUEST 
Bus data invalid 




T16 


Controller resets READY 




T17 


Controller sets READY 




T18 
T19 
T20 


Bus data valid byte 1 
Host sets REQUEST 
Controller resets READY 




T21 


Controller sets READY 




TIMING 




ACTIVITY 


TIMING 


N/A 


T22 


Host resets REQUEST 


T21-T22>0 uS 


N/A 


T23 


Bus data invalid 


T21-*23>0 uS 


T2-*T3>0 uS 


T2<f 


Controller resets READY 


20<T22-T2<K100 uS 


T3-T<K1 uS 


T25 


Controller sets READY 


20<T24-»T25<100 uS 


T4-T5>20 uS (500 uS nom.) 


T26 


Bus data valid byte 2 


N/A 


T5-tf6>0 uS 


T27 


Host sets REQUEST 


T25-*T27>0 uS 


T5-*T7>0 uS 


T28 


Controller resets READY 


T27-T28< 1 uS 


20 T6-*T8 100 uS 


T29 


Controller sets READY 


T28-**29>20 uS (500 nom.) 


20<T8-*9<100 uS 


T30 


Host resets REQUEST 


T29-ff30>0 uS 


N/A 


T31 


Bus data invalid 


N/A 


T9-*ll>0uS 


T32 


Controller resets READY 


20<T30— T32<100 uS 


Til— T12<1 uS 


T33 


Controller sets READY 


20<T32-»T33<100uS 


T12-*13>20 uS (500 uS nom.) 


T3<f 


Bus data valid byte 3 (LSB) 


N/A 


T13-T10>0uS 


T35 


Host sets REQUEST 


T33-T35>0 uS 


T13-T15>0uS 


T36 


Controller resets READY 


T35-T36<1 uS 


20<m-^16<100 uS 


T37 


Controller sets READY 


T36-iT37>20 uS (500 nom.) 


20<T16-rfT17<100uS 


T38 


Host resets REQUEST 


T37— T38>0 uS 


N/A 


T39 


Bus data invalid 


T37-*39>0 uS 


T17-T19>0uS 


T40 


Controller resets READY 


20<T38-tf*0<100uS 


T19-T20<1 uS 


T<fl 


Controller sets READY, 


T40-T41 (5-00 sec.) 


T20-T21 >20 uS (500 nom.) 




search complete, 
target block found 





ON LINE 
REQUEST 



X Don ' t Care 
\T2 XTJ 



READY 



/ T3 T» \ / TT 



£XCE P T I ON 

DATA BUS -777J&? — sTTf Test ^77///////A 



Self- 
Te s t ing 



\ 



T8 



XFER 



ACK 

dTrc 

RESET 



>/////////////////////, 



Read Status 
comma rid 
i ssued to 
ob ta i n 
results of 
Self Test 
I & I I 





ACTIVITY 


TIMING 


n 


Host command to bus 


N/A 


T2 


Host sets REQUEST 


Tl-T2>0uS 


T3 


Controller resets READY 


T2-T3<1 dS 


T4 


Controller sets READY 


T3-*T4>20 uS (500 uS nom.) 


T5 


Host resets REQUEST 


T4— T5>0 uS 


T6 


Bus data invalid 


T4-»T6>0 uS 


17 


Controller resets READY 


20 uS<T.5— T7< 100 uS 


n 


Controller sets READY 


T7-*T8>2QuS 



Figure 19. Run Self Test I & II. 
37 



CAUTION 

Self test II writes to the cartridge. Ensure that only a scratch tape 
cartridge has been installed. v 



1. Speed Test - Monitors tachometer pulses to verify tape speed. 

Fail = Status Byte 3 = 23 = Speed error. 

= Status Byte 4 = 01 = Test 01. 

2. Sensor Test -Rewind the tape, detects BOT, and moves forward to ensure 

that the sensors detect when the load point is passed. 

Fail = Status Byte 3 = 23 = Sensor error. 

= Status Byte 4 = 02 = Test 02. 

3. Write Test - This test writes 16 data blocks followed by 16 filemarks 

and verifies internal write completion for each block. 

Fail = Status Byte 3 = 22 = Write/Read error. 

= Status Byte 4 = 03 = Test 03. 

= Status Byte 5 = 01 = Speed or sensor error. 

= 03 = Write timeout error. 

4. Read Test -This test verifies read data, read filemark, and gap detect. 

Fail = Status Byte 3 = 22 = Read error. 

= Status Byte 4 = 04 = Test 04. 

= Status Byte 5 = 01 = Sensor or speed error. 

= 02 = Overrun detector error. 
= 03 = Read timeout*. 
= 04 = Unable to read*. 
= 05 = Unable to read filemark. 
= 06 = Gap detect failure. 
* If write protected cartridge is used with Self Test II, 
Test 4 will fail here, and status Byte will indicate write 
protect status. 

5. Erase Test - This test erases a portion of tape from BOT, and verifies 

that it is erased. 

Fail = Status Byte 3 = 22 = Write/Read error. 

= Status Byte 4 = 05 = Test 05. 

= Status Byte 5 = 01 = Speed or sensor error. 

= 03 = Erase error. 

6. Write Test - This test verifies single block write function. 

Fail = Status Byte 3 = 22 = Write/Read error. 

= Status Byte 4 = 06 = Test 06. 

= Status Byte 5 = 01 = Speed or sensor error. 

= 03 = Write timeout. 



38 



7. CRC Test 
Fail 



- This test verifies the CRC check function, and performs a 
positioning test. 



Pass 



Status Byte 3 
Status Byte 4 
Status Bvte 5 



Status Byte 3 
Status Byte 4 
Status Byte 5 



= 22 = Write/Read error. 

= 07 = Test 07. 

= 01 = Speed or sensor error. 

= 02 = Position error. 

= 03 = CRC failed. 

= 11 = Self Test complete. 
= 07 = Test 07. 
= 00 



No error. 



This concludes Self Test II. If all the tests are passed, the tape is erased and 
rewound to BOT, and the Self Test complete status can be found by issuing a Read 
Status command, If and error occurred, the test is stopped at that point, and the 
error status defined, as shown above. 

Self Test II is a functional verification of the 540, and may be used as an incoming 
test or as an isolation test of a specific drive failure. It allows the system to 
verify quickly that the 540 drive is functioning. 



39 



40 



SECTION 3 
ERROR PROCESSING & RECOVERY 



INTRODUCTION 



The 540 formatter provides extensive error processing and recovery sequences which 
greatly reduce the software effort required to interface the formatter with the 
host. The information in this Section is only intended to be an introduction to 
the basic principles of error processing and error recovery for the 540. 

The formatter provides statistical information on the number of errors it has auto- 
matically processed. When determining system performance, during the evaluation 
Ehase, these statistics can be very useful. Table 5 summarizes the Exception Status 
ytes provided by the formatter in accordance with QIC-02. 

Table 5. Exception Status Bytes. 



ByteO 


Bytel 


Status 


Description Result 


110X0000 


00000000 


No Cart- 
ridge 


Drive selected has Fatal 

no cartridge when 

BOT, RET, Erase, 

Write, WFM, Read 

or RFM was issued 

or cartridge was 

removed while 

selected. 


11110000 


00000000 


No Drive 


Tape drive selected Fatal 
not present when BOT, 
RET,Erase, Write, WFM 
Read, or RFM was issued. 


10010000 


xoooxooo 


Write 
Protected 


Tape drive selected Fatal 
contains safe (write 
protected) cartridge 
when Erase, Write, or 
WFM was issued. 


10001000 


00000000 


End of 
Media 


Tape passed early Contin- 
warning hole of last uable 
track during Write 
command. 


100X0100 


10001000 


Read or 

Write 

Abort 


Same block rewritten Fatal 
16 times during Write 
or WFM command, 
or unrecoverable re- 
position error occurred 
during Write, WFM, Read 
or RFM command. 



41 



Table 5. Exception Status Bytes. 



ByteO 



Bytel 



Status 



100X0100 



00000000 



Read 
Error Bad 
Block 
Transfer 



100X0110 



00000000 



Read 
Error 
Filler 
Block 



100X0110 



100X1110 



100X0110 



10100000 



10100000 



00000000 



100X0001 



00000000 



XXXX0000 1100X000 



Read, 
Error, 
No Data 

Read 
Error 
No Data 
&EOM 

Read 
Error 
No Data 
&BOM 



File 
Mark 



Illegal 
Command 



Description 

Tape returns to BOT. 



Same block with 16 
retries failed to 
recover block without 
CRC error; last block 
transferred contained 
filler data to keep 
total block count 
correct. 

No recorded data 
detected on the tape. 



No recorded data 
detected on the tape; 
logical EOT holes on 
last track encountered. 

No data detected; 
failed to recover next 
or subsequent blocks; 
during reverse reposi- 
tion, BOT holes in 
first track encountered. 

File Mark block is 
read during Read or 
RFM command. 

One of six attempts 
were made: 

a. To select multiple 
drives 

b. To change Drive 
select during a Read/ 
Write with tape not at 
BOT 

c. To request BOT, 



Result 



Same block retried 16 Contin- 

-~ -*» iww.w*. unv/vxv uauic 

without CRC error; last 
transfer contained data 
from erroneous data 
block for off-line 
reconstruction. 



Contin- 
uable 



Contin- 
uable 



Contin- 
uable 



Contin- 
uable 



Contin- 
uable 



Fatal 



42 



Table 5. Exception Status Bytes. 



ByteO 



Bytel 



Status 



XXXX0000 1000X001 



Power 



Description Result 

Retension, or Erase 
simultaneously. 

d. To request Write, 
WFM,Read,or 
RFM with On-line off. 

e. To issue command, 
other than Write or 
WFM during Write 
command. 

f. To issue command, 
other than Read or 
RFM during Read 
command. 

g. To issue any non- 
implemented command. 

Power On Reset or a Fatal 
Reset by host occurred. 



NOTE 

Bytes 2 and 3 (DEC) are the data error counter. Bytes 4 and 5 (URC) 
are the underrun counter. 

WRITE BUFFER UNDERRUN 

A Write buffer underrun should be avoided because it lowers the data storage ca- 
pacity of the tape and because it terminates the tape motion, resulting in a tape 
repostion delay before writing can resume. 

Tape streaming implies continuing tape motion with small gaps between data blocks. 
Therefore, the host must maintain an uninterrupted transfer of data blocks to the 
540 formatter. If a full Write buffer is not available to the Write channel when it 
is required by the formatter, a Write buffer underrun condition occurs and is logged 
in the statistical counters of the formatter. The formatter then initiates a last 
block sequence by rewriting the last data block. If a full Write Buffer is not avail- 
able before the Read data channel finishes checking the last data block the last 
block sequence is completed, tape motion is stopped, and a write Reposition is in- 
itiated. 

A complete last block sequence requires 0.528-inches to rewrite the last block, plus 
0.300-inches for the extended gap. The data throughput decrease that results from 
a Write buffer underrun at 90 ips is 0.98-inch per 1.76 blocks. 

Read-After-Write Errors 

It requires a density of 10,000 flux changes per inch (fci) to provide the 540 with 
its high-capacity storage. With this density it would be ideal for all recording 
conditions to be perfect. However, this state is seldom achieved. Therefore, the 

43 



540 formatter is designed to accommodate occasional data errors. To ensure that 
data is written correctly, a Read-After-Write check is made on each block of data 
immediately after it is written. If an error is found, the block is rewritten In 
order to support this Read-After-Write check, the three Write data buffers are 
allocated in this sequence: 

o Buffer one stores the block that k h^.ino written 

o Buffer two stores the block being checked by the Read-After-Write, so 
data remains available for rewritting. 

o Buffer three stores the next data block transferred by the host. 

To perform Read-After-Write checking, the tape drive head is designed with two 
gaps, one for writing and one for reading. These gaps are separated by a distance 
ot U.3-incn. For tape streaming, the inter-record gap length is only 0.013-inch- 
therefore, the formatter must begin writing the next record before the previous 
record has been completely verified by the Read-After-Write. 

Read-After-Write error recovery is automatically processed by the formatter Be- 
cause this process is invisible to the host, a statistical counter is provided to inform 
the host of the number of blocks automatically rewritten by the formatter Each 
rewritten block subtracts one block from the total capacity of the tape. Because 
each Error Recovery sequence normally rewrites two data blocks, the statistical 
counter normally contains an even number which usually represents one half the 
number of soft errors. 



READ BUFFER UNDERRUN 

l u n i? r S? al Read °P erations > the formatter locates a block of data, transfers it to 
the buffer memory in the formatter, and performs a CRCX check for errors. If no 
error occurs, the block of data is transferred to the host. The formatter contains 
three buffer memories. One is allocated to the Read Channel, one to the host, and 
one is held in reserve to be used if the host system temporarily gets behind the 
transfer throughput rate of the Read channel. This buffer memory configuration 
provides a 1-block buffer that allows short-term host system contentions before 
the Read operation overruns the buffer memories in the formatter. 

If the host system, with the three buffer memories, fails to stay ahead of the Read 
channel, a Read buffer underrun occurs. This condition arises when the Read chan- 
nel has located the next block of data and none of the three, buffer memories in 
the formatter are available for data storage. To prevent the loss of that block, the 
formatter must stop the tape. The formatter then performs a Read reposition se- 
quence and then resumes the normal read operation sequence, A statistical counter 
is provide in the formatter to keep track of the number of Read buffer underrun 
occurrences. 

Read Data Errors 

The formatter verifies Write data with a Read-After-Write check, because there are 
a large number of variables associated with reading data that can result in temporary 

44 



Read data errors. The error recovery process internal to the formatter rereads the 
Block-In-Error(BIE) up to 20 times during error recovery before informing the host 
that an unrecoverable Read error has been detected. The process of rereading a 
BIE is referred to as Soft Error Retry (SER) sequence. This process stops the 
tape, performs a Read reposition sequence, then continues the normal Read sequence. 

If the error is a BIE and is not recovered after 20 tries, the formatter transfers the 
BIE, if it can be located, terminates the Read operation, and alerts the host that 
the transferred BIE has an unrecoverable Read error. Unless aborted, an available 
data block is always transferred. If another block, rather than the BIE is trans- 
ferred, the host is alerted to this fact. 

Each SER sequence increments, by one, a statistical counter in the formatter. 
During a Read operation, data blocks with CRC errors that were rewritten during 
the Write operation are ignored. 

Read Sequence Errors 

The formatter appends a block address byte to each data block written on the tape. 
Blocks rewritten because of a Read-After- Write detected error, alter the normal 
sequence of the blocks written on tape. 

During Read operations, a block sequence error can be caused by encountering a 
block that was read from tape without a CRC error, but with an unexpected address. 
Block sequence errors cause the formatter to perform an SER sequence. The SER 
sequence for a Read sequence error is the same as for a Read data "error. If the 
limit of 20 SER sequences is exceeded without re-establishing the proper block 
address, the formatter transfers the BIE, if it can be located; terminates the Read 
operation; and alerts the host that the transferred BIE has an unrecoverable read 
error. Unless aborted, an available data block is always transferred. If another 
block, rather than the BIE is transferred, the host is alerted to this fact. 

READ OR WRITE ABORT ERRORS 

A Read abort or Write abort prevents a Read or Write sequence from being com- 
pleted. An abort is done when, after 16 rewrites of the same block, there is an 
unrecoverable reposition error. 

NO DATA DETECTED ERRORS 

The formatter searches a length of tape, equal to approximately 32 block times, for 
a specific block on the Read channel. If the block is not found, the formatter 
performs a Read reposition sequence and repeats the search up to 20 times. If 
the block is still lost, the formatter alerts the host that there is an unrecoverable 
data error due to no data being detected, and does not transfer a block of data. 



45 



46 



SECTION 4 
REPOSITION TIMING 
INTRODUCTION 

There are two types of Write buffer underruns. Type 1 allows continuation of the 
streaming mode. Type 2 is followed by a reposition operation, which is conducted 
by a Write buffer underrun handling routine. A normal Write operation and the 
two types of Write buffer underrun conditions are shown and described in Figure 
20. A flow chart of a Write buffer underrun routine is shown if Figure 21. 



Type 1. Write Buffer Underrun Event Sequence 

a. Host system fails to fill buffer in one block 

time, 
b Last Block (N) is rewritten. 

c. Host fills buffer with block N + 1 while 
block N is being rewritten. 

d. Tape keeps streaming and writing is con- 
tinued with block N + 1. 

Type 2. Write Buffer Underrun Event Sequence 

a. Host system fails to fill buffer in one block 
time. 

b. Block N is rewritten, but host system has 
not yet transferred block N + 1 to buffer. 

c. Formatter writes 0.3-inch gap. 

d. Tape motion ramps down and stops. 

e. Formatter waits for host system to load 
buffer. 

f. When host system has filled buffer, tape 
motion begins in opposite direction and 
tape is run back approximately 10 blocks. 

g. Tape motion stops briefly, then is reversed 
to original direction of tape motion during 
Write operation. 

h. Formatter scans incoming bit stream from 
Read logic for block address of last block 
written. 

i. When block address is found, formatter 
searches for extended gap. 

j. When extended gap is found, formatter 
appends another 1 ms of gap, followed by 
standard 528.5-byte block format (512 user 
data bytes), which contains block N + 1. 

Figure 20. Write Buffer Underrun Events. 

47 



WRITE 

BLOCK TO 

TAPE 



WRITE 

BLOCK N+1 

TO TAPE 




ETC. 



DELAY 

10 
BLOCKS 



DELAY 
1 MS 



STOP 
TAPE 



REVERSE TAPE 
DIRECTION 



WRITE 

EXTENDED 

0.3-INCH 

GAP 



STOP 

TAPE 

MOTION 




YES 



REVERSE TAPE 
DIRECTION 



CHECK FOR 

LAST BLOCK 

ADDRESS 



RESUME WRITE 

OPERATION 
STARTING WITH 

TRAILING END 
OF 0.3-INCH GAP 



Q 




YES 




YES 



Figure 21. Write Buffer Underrun Flowchart. 



48 



WRITE BUFFER CRITICAL TIMING 

To maintain tape drive operation in a streaming mode without logging a Write buffer 
underrun on the statistical counter, a complete 512-byte transfer of user data must 
be accomplished with 5.8 ms. 

If the host fails to respond within one block time, the formatter rewrites the last 
block from the host. The host then has an additional block of Write time to fill a 
Write buffer, before the formatter drops out of the streaming mode. The critical 
time elements are shown in Figure 22. 



COMPLETION OF 
FIRST BLOCK 
TRANSFER 



HOST MUST COMPLETE 
SECOND BLOCK 
TRANSFER BY THIS 
TIME OR FIRST BLOCK 
IS REWRITTEN 



FAILURE OF HOST TO 
TRANSFER SECOND BLOCK 
BY THIS TIME CAUSES A 
REPOSITION OPERATION 



TIME DEPENDS 90 IPS 

ON HOST FILLING 
FIRST BUFFER 



'1—^*2 
> 5.8 MS 



'2 -'3 

> 5.8 MS 



Figure 22. Critical Write Timing Elements. 
Write Reposition 
The timing sequence of a Reposition is shown in Figure 23. 



& 



v , t 



BLOCK N WRITTEN 
BLOCK N REWRITTEN 





-CAPSTAN STOP 



Tl to T2 = 1.3 sec 



Figure 23. Reposition Timing Sequence. 
49 



SECTION 5 

CONFIGURE OPTIONS 

JUMPER CONFIGURATION 

The select drive jumper configuration with enhanced formatter board (P/N 940524) 
is shown below: 

NNNN W6/W7 Select 

0001 In/In Drive 

0010 Out/In Drivel 

0100 In/Out Drive 2 

1000 Out/Out Drive 3 

The parity jumper configuration with enhanced formatter board is shown below: 

W8 W9 W10 Parity 

In Out In Enabled 

Out In N/A Disabled 



50 



cipher 



P.O. Box 85170 

San Diego, California 92138 

Telephone: 1-800-4-CIPHER 

TWX: 910-335-1251 



799905-005 
Revision A 

Copyright © Cipher Data Products, Inc. , 1988. All rights reserved. J u ' V 1 987