400112 00A ACB 3530A Streaming Tape Controller Users Manual Nov86 pdf

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ACB-3530A User's Manual

%"

Streaming Tape Controller

SCSI to QIC-36

Novem ber1986

@]

adoptee, inc.

_ . _

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TABLE OF CONTENTS

SECTION PAGE

1.0

2.0

3.0

INTRODUCTION. • • . • • • •

1.1 ACB-3530A FEATURE SET.

.

..

.

. .

...

REFERENCE DOCUMENTS. • • • . • • .

ACB-3530A CONTROLLER BOARD L~YOUT.

• • 1-1

· • 1-1

· . 1-2 1.2

1.3

1.4 PRODUCT SPECIFICATION • • •

1.4.1 PHYSICAL DIMENSIONS • .

. . . 1-4

. . . . . . . 1-4

1.4.2

1.4.3

POWER REQUIREMENTS. . • • •

ENVI RONMENTAL REQUI REt-1ENTS.

THEORY OF OPERATION • • • • • •

2.1 ACB-3530A ARCHITECTURE • .

2.2 MICROCODE STRUCTURE. •

2.3 SELF TEST. • • • . • • • • .

INSTALLATION. • • • • • • • • • • • • • .

3.1 UNPACKING. • . • • . • .

3.2 PREPARATION OF INSTALLATION AREA.

3.2.1 MOUNTING CONSIDERATIONS • • • • . • .

· . 1-4

• • 1-4

· • 2-1

• . 2-2

2-4

· • 3-1

· . 3-1

· • 3-1

3.2.2 RF CONSIDERATIONS . . . • 3-2

3.3

3.4

ACB-3530A CABLING. . .

3.3.1 ACB-3530A POWER CONNECTOR, J4 •

ACB-3530A CONFIGURATION. . .. . . .

3.4.1 SCSI BUS ADDRESS • •

3.4.2 SCSI BUS PARITY DISADLE • • .

3.4.3 SCSI BUS PARITY OPERATION • • • . 3.4.4 SCSI RECONNECT.

i

3-2

3-3

• .. 3-4

· • 3-4

· • 3-5

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SECTION PAGE

.. 3-5

4.0

5.0

3.5 POWERING ON THE ACB-3530A • • • . • •

QIC-36 1/4" STEAMING TAPE INTERFACE .

4.1 QIC-36 INTERFACE SIGNALS • • .

4.2

4.3

BLOCK FORMAT • •

4.2.1 FILE MARKS.

TRACK LAYOUT • • • •

4.4 TAPE MEDIA DEFECT HANDLING • • • .

SCSI INTERFACE DESCRIP·rION. • • • •

5.1 GENERAL DESCRIPTION OF SCSI • • • •

5.2 SCSI BUS SIGNALS • • •

5.3 SCSI BUS PHASES • • •

5.3.1 BUS ~REE PHASE.

5.3.2

5.3.3

5.3.4

5.3.5

5.3.6

ARBITRATtON

PHASE •

SELECTION

PHASE •

RES

ELECTION

PHASE •

INFORMATION TRANSFER PHASE. •

5.3.5.1 COMMAND PHASE. • • •

5.3.5.2 DATA PHASE • • . • • • .

5.3.5.3 STATUS PHASE.

5.3~5.4 MESSAGE PHASE.

SCSI BUS PHASE SEQUENCING ..

• 4-1

4-1

4-3

· 4-3

• 4-4

.. • 5-1

.. .. 5-1

.. 5-2

.. . 5-4

.. 5-5

· 5-5

• 5-5

.. 5-6

• • 5-6

• • 5-8

· • 5-9

• 5-9

5.4 BUS CONDITIONS • • • • • . • • • • • . . • . .

5.4.1 ATTENTION CONDITION . . . . • •

5.4.2 RESET CONDITION AND ABORT MESSAGES.

.. 5-9

· 5-11

.. 5-11

· 5-11

5.5 SCSI BUS TIMING • 5-11

ii

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SECTION

6.0

5.6

5.7

5.8

COMMAND DESCRIPTOR BLOCK •

COMPLETION STATUS BYTE

SCSI MESSAGE SYSTEM

..

. .

. . . .

.

5.8.1 SCSI MESSAGE DESCRIPTION

COMMAND DESCRIPTIONS. • • • • •

6.1 TEST UNIT READY COMMAND.

6.1.1 POSSIBLE ERROR STATES

6.2 REWIND COMMAND • • • • . • • • • •

6.3

6.4

6.5

6.6

6.2.1 POSSIBLE ERROR STATES •

REQUEST SENSE COMMAND. • • •

6.3.1

6.3.2

6.3.3

POSSIBLE ERROR STATES •

UNIT SENSE INFORMATION.

SENSE KEYS • • • • •

READ BLOCK LIMITS COMMAND.

SET PARAMETERS COMMAND . • •

READ COMMAND • • • • ~ • • • •

. .

.

,

.'

6.7 WRITE COMMAND. • • • • •

.

. .

. . .

6.7.1 FORCED STREAMING.

6.7.2 ENCOUNTERING END OF MEDIA •

6.7.3 WRITE ERRORS DURING BUFFERED MODE.

6.7.4 MEDIA DEFECT HANDLING • •

i i i

PAGE

5-15

5-16

5-17

• . 6-1

· • 6-1

. 6-2

6-2

• • 6-3

· • 6-4

• • 6-4

• . 6-4

· • 6-7

. 6-9

• • 6-9

· • 6-10

· • 6-11

6-1·2

• 6-13

· . 6-14

· 6-15

• • 6-16

· 6-16

• . 6-1 7

· 6-18

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SECTION

6.8 WRITE FILE MARK COMMAND • • • .

6.8.1 POSSIBLE ERROR STATES.

6.9 SPACE COMMAND. • • • • • • • •

6.10 INQUIRY COMMAND.

6.11 VERIFY COMMAND.

6.12 RECOVER BUFFER DATA COMMAND • • . .

PAGE

• • • 6-19

· . 6-20

• 6-21

· • 6-22

• • 6-23

• • 6-24

• • 6-25

· • 6-25

.

· • 6-26

6-27

6.13 MODE SELECT COMMAND • •

· .

.

16.13.1 POSSIBLE ERROR STATES • •

6.14 RESERVE UNIT COMMAND

_·

6.14.1 POSSIBLE ERRO.R STATES.

6.15 RELEASE UNIT COMMAND

_·

_{· ·}

_·

.

_·

6.16 ERASE COMMAND.

. .

. ·

_·

_{· ·}

_·

6.17 MODE SENSE COMMAND

.

_·

_{· · ·}

6.18 LOAD/UNLOAD UNIT COMMAND • • •

6.18.1 POSSIBLE ERROR STATES. • .

iv

400112-00A

·

· · ·

·

· · ·

·

· • 6-27

6-30

· ·

6-31

· ·

6-31

6-32

·

6-32

·

6-33

· ·

6-33

· ·

6-34

• • 6-34

6-35

· • 6-36

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LIST OF TABLES

TABLE

3-1 ACB-3530A CONFIGURATION JUMPERS, J6 • •

4-1 QIC-36, J1, CONNECTOR PIN ASSIGNMENTS.

5-1 SCSI CONNECTOR, J3, PIN ASSIGNMENTS

5-2 INFORMATION TRANSFER PHASES • • • •

~

.

"".' ~

.

PAGE

• 3-3

• 4-1

5-3·

• 5-7

5-3 SCSI MESSAGES SUPPORTED BY THe ACB-3530A. _{• 5-17}

6-1 ACB-3530A SCSI COMMAND SET.

6-2 ACB-3530A SENSE KEYS.

6-3 SPACE SEARCH CODES. •

LIST OF FIGURES

FIGURE

ACB-3530A BOARD LAYOUT. •

2-1 ACB-3530A BLOCK DIAGRAM

2-2 ACB-3530A CONTROLLING FIRMWARE.

.

3-1 ACB-3530A SYSTEM CABLING. • • • •

3-2 POWER CONNECTOR, J4, PIN ASSIGNMENT

4-1

4-2

5-1

5-2

5-3

5-4

orC-ll AND QIC-24 BLOCK FORMAT. .

1/4" TAPE LAYOUT.

TYPICAL SCSI CONFIGURATION.

REQ/ACK HANDSHAKE • . . •

SCSI BUS PHASE SEQUENCING ..

SCSI BUS TIMING • .. . .. •

v

400112-001\

• 6-1

. . . 6-7

• • • 6-21

PAGE

· 1-3

.

• 2-2

• 2-3

• 3-2

3-3

4-3

· 4-4

5-2

· 5-8

• 5-10

· 5-12

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FIGURE

5-5 CLASS 0 COB SUPPORTED BY THE ACB-3530A.

5-6

5-7

6-1

6-2

6-3

6-4

6-5

COMPLETION STATUS BYTE. • • •

IDENTIFY MESSAGE. • • •

TEST UNIT READY COMMAND

REWIND COMMAND.

.

. .

REQUEST SENSE COMMAND • •

SENSE INFORMATION • • •

READ BLOCK LIMITS COMMAND

6-6 READ BLOCK LIMITS DATA RETURNED • • • •

6-7 SET PARAMETERS COMMAND. • . • • • •

6-8 READ COMMAND. • • • •

6-9 WRITE COMMAND • • • •

6-10 WRITE FILE MARK COMMAND .

6-11 SPACE COMMAND • •

6-12 INQUIRY COMMAND

.

. .

.

. .

.

PAGE

· 5-15

• 5-16

5-18

.'

.

• 6-2 • 6-3

• 6-4

· 6-5

6-9

• 6-9

• 6-10

• 6-12

• 6-14

· 6-19

. • 6-21

• 6-23

6-13 INQUIRY DATA. • • • .

.

. .

.

• • 6-24

6-14 VERIFY COMMAND. • • •

6-15 RECOVER BUFFER DATA COMMAND • •

6-16 MODE SELECT COMMAND • • • • • • • •

. .

6-1 7 MODE SELEC'r CONFIGURATION DATA BLOCK. •

6-18 RESERVE UNIT COMMAND. •

6-19 RELEASE UNIT COMMAND.

6-20 ERASE COMMAND • • •

. . .

.

6-21 MODE SENSE COMMAND.

6-22 LOAD/UNLOAD COMMAND •

400112-00A

vi

• 6-25

• 6-26

• • 6-27

· 6-29

. • . . • . 6-31

• • • e e _ • 6 ... 32

· 6-33

6-34

• 6-35

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1.0 INTRODUCTION

The Adaptec ACB-3530A streaming Tape Controller ~oard interfaces

a 1/4" streaming tape drive using the QIC-36 interface to any

host interface compatible with the ANSI X3.331 - 1986 Small

Computer System Interface (SCSI).

1.1 ACB-3530A FEATURE SET

• Full SCSI specification, ANSI X3.33l - 1986 compatibility.

Connects to any SCSI standard host adapter.

- SCSI bus arbitration and· disconnect/reconnect support.

Overlapped disk/tape operation capability with multitasking

I/O SUbsystems.

• Buffered write and immediate command completion support.

Data buffering and immediate completion mode for streaming on

systems that do not support SCSI bus disconnect/reconnect.

• QIC-24 and OlC-11 media format support.

Capable of reading and writing OIC-24 and OlC-1l format tapes.

• 16-Bit CRe on each record and SCSI bus parity.

Data integrity is assured by reading the data and checking CRe

immediately after it is

written.

eRe

is also

checked on

tape

reads. In addition, SCSI bus parity is checked or generated

on all bus transfers.

• Automatic tape defect handling.

Media defects detected by the controller from read after write

will result in the data being rewritten in the next sequenti~l

block.

~ Reserve/Release.

The tape drive can be reserved by an attached host to restrict

other host accesses to the data.

1.2 REFERENCE DOCUMENTS

• ANSI X3.331 - 1986 Small Computer System Inter.face

Specifica-tion.

• QIC-24 Specification: Proposed standard for data interchange

on streaming 1/4" drives.

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o QIC-ll Specification: Proposed standard for data interchanqe

on streaming 1/4" drive~.

o QIC-36 Specification: 1/411 streaminq tRpe drive hasic

inter-face.

1.3 ACR-3530A CONTROLLER BOARD LAYOUT

The dimensions and component layout of the ACB-3530A is shown in

Figure 1~1. This diaqram is referred to later in the manual for

the location of the interface connectors, bus terminators, and configuration jumpers.

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....

0062

-iPLACES

---

I- 0.050

I~ 5.078

1

-+

I. _I

+

T

J1

.

64.:.0

-

-+ _-+

1

MeODE

SKT-27128

-r

5.500

0.900 iYP 2 PIJ,CES

6.4

--~

6.62

20

--"'- I " ' - - _{r - - -}

-5

tl200

5.500

l....n-AIC-32000

~"o

.19

JH

f

~ ~ L..J"\..- ,J7

- " - 8085 8156 AIC-010 Jc

Ale-300 0.950 TYP.

t - -HVCQ1

? PLACES

_t

!

1.075

+

B

-+

!

J

1.225

D

1:'2S

L

1

137"

I.

J3

I

1--+ _I--!

+-

J~

..

5.00

..

.5 078

...

4 _5.250 _-

...

-

~ I-OOSO

-

-()250

FIGURE 1-1. ACD-3530A BOARD LAYOUT

[image:10.613.33.548.31.752.2]

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1.4 PRODUCT SPECIFICATION

The ACB-3530A contro11eris designed to function under normal

operatinq conditions for electronic components. The form factor

is'such' that the controller can be mounted with the drive in most systems.

1.4.1 PHYSICAL DIMENSIONS

Length: 8.00 inches (18.1 em)

Width: 5.50 inches (14.6 cm)

Height: 0.75 inches ( 1.9 cm)

1.4.2 POWER REQUIREMENTS

+5 VCD + 5% at 1.8 Amps (max)

+12 VDC-+ 10% at 100 mAmp (max)

1.4.3 ENVIRONMENTAL REQUIREMENTS

Temperature (F/C):

Humidity (non-cond): Altitude:

OPERATING

32% ° to 131°/55°

10% to 95%

o

to 10,000 MSL

STORAGE

-40°/-40° to 167°/75°

10% to 95%

o

to 10,OOOMSL

Exhaust air flow may be required to keep the airon both sirles of

the board at or below the maximum operatinq temperature.

(12)

2.0 THEORY OF OPERATION

The ACB-3530A architecture

is

designed around the Adaptec controller chips~ the AIC-OIO and AIC-300. This architecture divides the controller into two basic components,~la data path and a control path. A block diagram of the ACB-3530A is shown in Figure 2-1.

2.1 ACB-35!OA ARCHITECTURE

The ACB-3530A data path carries data to and from the attached Q·IC-36 tape drive and host. Data is transferred in an asynchronous fashion from the host to/from the controller BK-dual-ported buffer RAM. The buffer dual-port addressing and port handshaking is controlled by the AIC-300. Odd bus parity is checked on data tranoferred into the buffer and generated on data trans ferred onto the SCS I bus. The dua l-ported bu f fer is designed to allow data to be written into one port (i.e., from the host) as i t is being read out from the other (i.e., to the tape) in a FIFO fashion.

Data is transferred between the RAM buffer and the AIC-OIO

sequencer using synchronous timing to assure streaming operation. Data is converted into a serial NRZ data stream in the OIC-24 for mat by the A Ie - 010. . Th e Q I C - 24 I Dan d d a t a fie 1 d s are the n appended with CRC information. This NRZ data stream is encoded into the GCR encoding scheme and written onto the tape. As data is being written, the ACB-3530 is also performing a eRC check on the data and will rewrite blOCKS if any errors are detected.

An eight-bit microprocessor is used to initialize and monitor the status of the data path and serves as the main component of the control path. The microprocessor drives the SCSI control lines to sequence through the various bus phases and decodes a 11 SCSI

commands. The microprocessor is further used in the SCSI

interface to report

all

errors encountered and to transfer messages to the host.

The microprocessor also performs the main controlling functions on the QIC-36 interface. These include trac'}{ select, motion control, and cartridge status (in or out).

(13)

SCSI BUS

AIC-500 SCSI INTERF.'\CE

AIe-·30G BUFFEI< CONTr"oL

CONTr<OL LOGIC

. AIC-010 SEQUENCER

AIC-32000 ...-. GCR

ENCODE/OECODE

[image:13.620.34.573.56.497.2]

TAPE CONTr<OL

FIGURE 2-1. ACB-3530A BLOCK DIAGRAM 2.2 MICROCODE STRUCTURE·

QIC-36 rAPE IN1ERFACE

The controlling microcode for the ACB-3530A is preprograrnmed in

16K of EPROM memory. This firmware contains a 11 routines

necessary to properly interface to the SCSI bus and the QIC-36 interface and to control the tape data path. Figure 2-2 shows a basic flow chart for the controller firmware.

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POWER UP RESET

HI\I<D

SCSI RESET

~

DIAGNOSTICS

---

IDLE lOOP:

•

SElECTION?

NO CHECK TARGET 10

YES

COMMAND REPROCESSING

r

SHARED SU8ROUTlNES

TAPE

~

WPITE DISCONNEC r,.

MOTION DATA . DATA RECONNECT

I

NORMAL EXIT mROP EXIT

~'J0 COMr-.l1r·ND COMPLETED

?

YES

CLEAN-UP POST PROCESSING

FIGURE 2-2. A~B-3530A CONTROLLING FIRMWARE

[image:14.618.57.567.41.777.2]

(15)

2.3 SELF TEST

-The self test function is automatically executed on the ACB-3530A

upon power-up or after an SCSI reset. The self test executes in

300 ms, and during this time the controller will not respond to

any selection requests from the SCSI bus. During the test, the

red LED on the front of the board will be illuminated. If the

self test is failed, the LED will blink rapidly, at a rate of

approximately 4 Hz.

The loop-an-self test feature is invoked on the ACB-3530A by

holding SCSI ACK true while SCSI BSY is floating (false). During

this condition, the self test function will loop on itself.

(16)

3.0 INSTALLATION OF THE ACB-3530A

The ACB-3530A is designed to provide the performance and

"

flexibi lity required to reliably operate a QIC-36 1/4'" tape dri ve

for streaming backup of system data. Some basic installation

steps are required to assure proper board operation.

3.1 UNPACKING

The ACB-3530A is shipped in a protective carton with shock-absorbing and static protection material completely surroundinq

the ca rd. The ca rton shou ld be exa mined for externa 1 da mage as

i t is opened. The cards are physically inspected prior to

packaging, any damage noted should be reported immediately.

CAUTION: ALL CIRCUIT BOARDS CONTAININGVLSI CIRCUITRY HAVE SOME

SENSITIVITY TO ELECTROSTATIC DISCHARGE. THE ACB-3530A IS NO

EXCEPTION. PROPER HANDLING PRECAUTIONS. INCLUDING PERSONNEL AND

WORK SURFACE GROUNDING, SHOULD

BE

TAKEN TO PREVENT CIRCUIT STRESS

WHICH CAN CAUSE COMPONENT F~ILURE.

3.2 PREPARATION OF INSTALLATION AREA

The ACB-3530A is generally designed into the physical host system

or a peripheral subsystem. Proper attention should be given to

the location of the ACB-3530A to assure that necessary

ventilation, ~nstallation clearances, and cabling paths are

provided.

3.2.1 MOUNTING CONSIDEP~TIONS

The ACB-3530A can be physica lly mounted using the four mounting

holes. These holes are in locations compatible with standard

5-1/4" Form Factor for.mounting onto the drive. The controller can

also be mounted onto custom designed brackets for alternate

mechan i ca 1 requi rements. Ca re must be ta ken, however, to

consider the physical forces the system will be subject to. No

conductive material should come in contact with the ACB-3530A PC

card.

(17)

3.2.2 RF CONSIDERATIONS

The J~CB-3530A and all other partially shielded electronic devices are sensititve to high power, high frequency or magnetic sources.

The con t ro lle r shou Id, be protected from such so~rces,:. In

particular, unshie lded switching, power supplies should be

ph Y sic a l l y i sola ted from a 11 e 1 e c t ron i c boa r d 5 and

interconnecting cables. Additional cable shieldinq may be

required' in some environments.

3.3 ACB-3530A CABLING

The ACB-3530A is connected into the host system or subsystem

using board connectors Jl, J3 and J4. The connectors are used as

follows:

Jl - 50 Pin QIC-36 Connector (Section 4.1)

J3 - 50 Pin SCSI Connector (Section 5.2)

[image:17.615.38.585.33.773.2]

J4- 4 Pin Power Connector (Section 3.3.1)

Figure 3-1 shows proper system cabling. Take care to note Pin 1

orientations of all connectors. These are easily found by

locating the square solder pad on the solder side of the PC board.

NOTE:

IF THE ACB-3530A IS NOT THE LAST CONTROLLER ON THE SCSI BUS,THE SCSI TERMINATORS, RN1, RN2, AND RN3, SHOULD BE REMOVED.

400112-00A

SCSI

HOST

ADAPTEI< J3

J4

J1 QIC-36 TAPE

Df<IVt:

FIGURE 3-1. ACB-3530A SYSTEM CABLING

(18)

3.3.1 ACB-3530A POWiR' CONNECTORj J4

Figure 3-2 shows the pin assignments for power connector, J4.

The suggested mating connector to J4 is AMP P/Nl-480424-0 or

equivalent.

+12'1

+12'1 RETURN

+5V RETURN

+5V

FIGURE 3-2. POWER CO~mECTOR. J4, PIN ASSIGNMENTS

3.4 ACn-3530A CONFIGURATION

The ACB-3530A requires a minimum of hardware setup.

The function of J6 through ,,110 is shown in Table 3-1. Sections

3.4.1 and 3.4.2 detail these functions.

TABLE 3-1. ACB-3530A CONFIGURATION JUMPERS, J6

J6 00 SCSI Bus Address 2°

J7 00 SCSI Bus Address 21

J8 00 SCSI Bus Address 22

J9 00 SCSI Parity Disable

JIO 00 Spare

3.4.1 SCSI BUS ADDRESS

The in s t a 11 a t ion 0 f j u m per s J 6, J 7 and J 8 set the add res sID 0 f

,the ACB-3530A on the SCSI bus. SCSI devices can have bus

addresses of zero to seven, however, no two devices m~y have th~

same address. A jumper installed indicates a logicalone bit

address.

[image:18.618.32.575.34.761.2]

(19)

3.4.2 SCSI BUS PARITY DISABLE

The installation of jumper J9 will disable the ACB-3530A odd bus

parity check on all data transferred from the host. If the

attached host dbes not ~enerate parity, parity must be disabled.

The ACB-3530A will always, generate odd parity on data transferred to the, host.

3.4.3 SCSI BUS PARITY OPERATION

The ACB-3530A incorporates full SCSI bus parity generation and

verification. The handling of parity errors by the controller is

detailed below.

Parity error on LD Message or Command Byte

A parity error on either an 10 message to the controller 6r on

the transfer of command bytes to the controller will result in

the command terminating after transmission of all six command

bytes with a Sense Key of 04h (Hardware Error) and Sense Byte 08,

bit 2 set.

Parity Error on Data to Controller During WRITE DATA

A parity error on data ,out to the controller during a WRITE DATA

command is latched and checked at the end 'of the transfer of each

blocK from the host. Detection of a parity error will result in

the command being terminated with a Sense Key of 04h and bit 2,

sense byte 09 set. The block which resulted in a parity error

will NOT be written onto the tape. The residue count will, as

usua 1, show the number of blocks remaining to be transferred to

the tape.

Parity Error on Message to Controller

On any Message Out to the controller, a parity error will cause the command in progress to be terminated with a Sense Key of 04h

and bit 2, sense byte 09 set. The message itself will be

ignored. This situation is always followed by a Status Out phase

(status

=

2), then by a Message Out phase, which terminates the

conunand.

-~-.~.... .~: .::-...

--

~ ... ---.

\lr,i't.l.at.or ~~t.ect:.e6 Errorj. In ai.;.. Cc.'s:::5. _ .. _~ ... :.' __ ::.:.:..~.": . . "

the command in progress terminating with 0. s::: :-.;::.~ !':: ; . : . : : .. : .:

(command aborted). For Read and Write commands, t:.~2-:~~:~_~

count will be valid.

(20)

For Read commands, any dat~ and/or status which resulted from "Lying Read" type operations (i.e., from the tape process being

ahead

at

the SCSI process) will be disregarded. The tape will

then be positioned at the end of the last record transferred to the host before the I n i t i a t o r Detected Error message was

received. ThUS, the host will be able to retry the operation by

backspacing the tape and rereading.

While transferring Data Out during a Read comma~d, the ATTN will

be checked between blocks to allow the host to notify the

controller of a parity error on Data In. It should be noted that

i f the host waits more than 128 blocks between the time i t detects a parity error on Data In and the time i t notifies the controller of this fact by raising ATTN and sending an Initiator Detected Error message, backspacing to recover from the error

will not be possible (as per current QIC-36 specification,

Reverse Space commando are limited to 128 blocks).

3.4.4 SCSI RECONNECT

When at tempting to reconnect after havi ng disconnected, the 3530A will wait 250 ms for the host to assertBSY after the

ACB-3530A has won arbitration for the bus. If the host does not

respond before the 250 ms expires, i t will clear the data bus and

check once more for BSY. If the host s t i l l has not responded,

the I/O operation is immediately terminated and no further attempts to communicate with the host will be tried without

rearbitration. See pages 5-6 and 5-12 in this manual for more

information on this feature.

3.5 POWERING ON THE ACB-3530A

The ACB-3530A, once properly cabled and configured, can be

powered-on. Power should not be applied to the controller i f

activity is present on the attached SCSI bus. The electrical

nature of the components typically used to drive this interface could interrupt bus activity.

If a cartridge is installed in the attached drive at power-on, the controller will rewind i t to BOT to prepare for read and write accesses.

If a cartridge is installed some time after power-on, i t will be rewound by the controller upon insertion.

The controller will present a Busy status to any access attempts made during the power-on cartridge insertion tape rewind.

(21)

4.0 QIC-36 1/4" STRE.1\MING TAPE INTERFACE

The QIC-36 interface provides a low-cost, high-performance,

standard interface for attaching a 1/4" stream1:,nq tape ·drive to intelligent controller/formatters. This section describes the interface between the ACB-3530A and a QIC-36 tape drive.

4.1 QIC-36 INTERFACE SIGNALS

The QIC-36 interface is implemented through a 50-pin dual-in-line header located at position J1 on the ACB-3530A. The suggested mating connector is 3M pIN 3425-60XX, 3425-70XX or equiv~lent.

Maximum cable length is 10 feet (3 meters).

The connector pins are numbered 1 to 50. All odd pins are signal returns and are connected to the controller board ground. Table

4-1 shows Jl pin assignments.

TABLE 4-1. OIC-36, Jl, CONNECTOR PIN ASSIGNMENTS

Return 1 0 0 3 0 0 5 0 0 7 0 0

9 0 0

11 0 0

13 0 0

15 0 0

17 0 0

19 0 0

21 0 0

23 0 0

25 0 0

27 0 0

29 0 0

31 0 0

33 0 0

35 0 0

37 0 0

39 0 0

41 0 0

43 0 0

45 0 0

47 0 0

Return 49 0 0

400112-00A 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 SIGNAL GO- REV- TR3- TR2- TR1- TRO- R8T- OS3- 082- 081- D80- HC- RDP- UTH- LTH- 8LD- CIN- U8F- TCH- WOA-WOA+ TDH- H8D- WEN- EEN-4-1 SOURCE

c

C C C C C C C C C C C D D D

o

D D C C C C C C DESCRIPTION

Tape Motion Enable Tape Direction Control Track Select 2~

Track Select 2

Track Select 21

Track SE! lect 2 0

Reset (Initialize Drive)

Reserved (not used)

Reserved (not us~d)

Reserved (not used)

Drive Select 0

High Write Current

Read Data (Pulse Output)

Upper Tape position Code

Lower Tape position Code

Drive Select Response

Cartridge In Place

Unsafe (No Write Protect)

Capstan Tachometer Pulse

write Data Signal

-Write Data Signal +

Threshold (35% Read Mrgn)

High-Speed Slew Select

Write Enable

Erase Enable

[image:21.620.44.585.52.779.2]

(22)

A detail of the QIC-36 interface signals follows:

Go (GO-): Assertion of GO- causes a start tape motion sequence in

the direction specified by the state of REV-.

Reverse (REV-): Assertion of REV- will cause tape motion in the

reverse direction i f GO- is asserted. Deassertion of REV- wi 11

cause tape motion in the forward direction.

Track Select (TRO-. TRI-. TR2-. TR3-): Assertion of the track

select signals will result in the selection of track 0 through 3,

on a four-track drive, or 0 through 8, on a nine-track drive.

Track selection is made through binary assertion of these lines

with TRO- the least signifi~ant.

Reset (RST-): Assertion RST- will cause the tape drive to

reinitialize. This sequence differs between drive vendors.

Drive Select (DSO-)/Drive Selected (SLD-): The assertion of OSO-selects the attached tape drive to allow all tape operations to

proceed. The drive selected signal (SLD-) will be asserted by the

drive in response to selection.

High Current (HC-): Assertion of HC- enables the tape drive to use a higher write current when writing to the drive.

Read Data Pulses (RDP-): Serial read data is passed to the

controller as a pulse for every flux change. Since no read enable

is required, Read Data Pulses will be present any time data passes

under the tape read head and DSO- is asserted.

Upper Tape Hole (UTH-)/Lower Tape Hole (LTH-): The UTH- and

LTH-signals are generated by the drive to indicate some media status.

The BOT, Load Point, Early Warning, and EOT tape holes are encoded

to produce an output code indicating specific positions of the

tape. .

Cartridge In (CIN-): The CIN- signal is asserted by the drive

when a cartridge tape is fully installed and 050- is asserted.

The line is deasserted when the cartridge is removed.

Un sage (USF-): The USF- signal is asserted by the drive to

indicate that the installed cartridge is 'not write protected.

This signal will be asserted when the write protect plug is in the

unsafe position and DSO- is asserted •

.

,

.'

Tachometer Pulses (TCH-): The tachometer pulses generated by the

rotation of the capstan motor inform the controller when the tape

is in motion and how fast. DSO- must be asserted for this signal

to be valid.

(23)

Write Data (WDA+, WDA-): WDA lines are differentia lly driven and

contain tape write data from the controller. WEN- must be

asserted prior to writing to the tape.

Threshold (THD-): Assertion of THD- invokes a 35% qualifying

amplitude for the read signal. This is typically used to

eliminate marginal tape recording areas.

High-Speed (HSD-): Assertion of HSD- causes 30 ips tape drive to

operate at 90 ips speed.

Write Enable (WEN-):

written to the tape.

Erase Enable (EEN-):

the full tape width asserted.

4.2 BLOCK FORMAT

Assertion of WEN- allows write data to be

Assertion of EEN- enables erase current to

err.! se head. 080- and TRO- mu~t a Iso be

The ACB-3530A is designed to read and write user data, control

information and file marks in the OIC-24 and orC-11 media

formats. Both media format standards are supported with a

512-byte block size and are shown in Figure 4-1.

BLOCK CRC NUMBER

BLOCK cr·:c

NU~}Pr:r~

FIGURE 4-1. OIC-II AND OIC-24 BLOCK FOR~mT

4.2.1 FILE MARKS

Data blocks can be used to create "marks" on the t.:\pe, typically

between recorded files. File marks are written to the tape when

specified by the host using a unique data pattern in the 5l2-byte

data field. The host can then use file marks as boundaries for

spacing and streaming reads.

' \

[image:23.615.34.571.157.765.2]

(24)

4.3 TRACK LAYOUT

Data is read and written in a serpentine fashion betwen the tape

early warning holes, Load Point and Early Warning. When the

controller encounters the end of a track, the tape reverses

direction' and "continues the read or write. Even-numbered tracks

are recorded while the tape is moving forward. Odd-numbered

tracks are recorded while the tape is moving backward. The

controller reports an overflow state when the end of the last

track is encountered (Early Warning). While writing on trackO,

[image:24.615.34.583.54.751.2]

the tape erase head will be activated ahead of the write data.

Figure 4-2 shows the layout of an entire 1/4" tape and the

relative location of the tape positioning holes.

fOf<WAf<U [)tl~fCfiON

ui f,\J'( Ifli,v'[l «().(ID( CiliA: GF

IN'I ShOWN j

rr<K5

-~.--4r--.-1

7 J .1

D

(,

2

-~--+-4r---=t===-' If,"b

-'4r-.4---$--f'HYSICf,L

lND 01 IAP[

· . ) l l " - I -.. - - - 4 S O ' - - - · - Y / ' - .... 1W·-._·lt!"'--wAf{NING

?ONl

I

lAr~LY

WArmiNG

HI (~Ir,~ IIII( ~

FiECOflDINC 'lJ1~,~JINC (., 1,,1'1

ZOOt ,(A4f fIULl:.,

I

I (),'C'

f>(liNI

I

lJ,UNI\!lf-JC

<.A ".J-!

l'U;,lllnr'J

i·'H,·:A(>.1 LIt 'Jlf' ,I JIf ~(.,

Uf I ",d,

FIGURE 4-2. 1/4" TAPE LAYOUT

4.4 TAPE MEDIA DEFECT HANDLING

The ACB-3530A checks each block on the tape for good eRC as it is

being written. However, since the tape read head trails the

write head by about 300 bytes, the CRe results for a given block

(block N) are not known until. the next block write has begun.

The controller, therefore, assumes that the previous block wi 11

check correctly and begins writing the next block as such.

If the CRC check should fail, typically due to a media defect, the

ACB-3530A will complete the current block write (N+l) and then

rewrite the previous block (N). This alternation between N is

achieved or 16 unsu6cessful writes have been attempted. If block

N were the last block to be written, it would be repeated until a

good CRe check is made. This results in the last block of each

write to be written at least twice.

This process is effective in that the ACB-3530A will not attempt

to read N+l until a valid read from block N is made.

(25)

5.0 SCSI INTERFACE DESCRIPTION

This section briefly describes the SCSI protocol implemented by

th~ ACB-3530A. The SCSI protocols are further defined in the

ANSI X3.33l - 1986 specification.

5.1 GENERAL DESCRIPTION OF SCSI

~he SCSI is a device-independent method of interfacing up to

eight host computers and peripheral devices. Device independence

relates to the ability to communicate with a number of peripheral types without regard to the physical characteristics of the device (i.e., number of tracks, tape capacity, etc.).

The SCSI interface, based on the IBM block multiplexer I/O

channel, provides optimum performance in to-host and

host-to-periphera 1 communication. . The SCSI is implemented through a 50-pin ribbon cable that is daisy chained to all attached hosts

and peripheral controllers. The SCSI can support up to eight

devices. A single device, such as a disk controller, can support

a number of peripherals. The daisy chained SCSI cable must be

terminated at both ends. Figure 5-1 shows the ACB-3530A in a

typical SCSI configuration.

Communication occur~ across the bus in a Request/AcknQwledge,

asynchronous fashion. The asynchronous bandwidth of the SCSI bus

is 1.5 Mbyte/sec maximum. When two devices communicate across

the bus, the device initiating "the command assumes an INITIATOR

role, the other device required to execute the command is

designated as the TARGET. Host computers are almost always

INITIATOR's, controllers are transferred and executed acrORS the

bus u sin 9 a n u m be r 0 f bus It ph a s e s. .. Th e ph a 5 e s d e t e r min e w hat

type of information (command, data, status, etc.) is being

transferred at any given time.

In order to execute a command, the INITIATOR (host) must first

gain control of the SCSI bus, this is accomplished through

arbitration. The host then selects the required controller.

From this point on, the controller determines all bus phases and

byte transfer~ The host interface must make no assumption

regarding the sequence of bus phases, as error conditions can

cause the controller to change the bus stat~ in the middle of

command and data transfers.

(26)

o·

50 PIN

f~IBBON

CABLE

AHA-15JO MULTIBUS

HOST ADAPIW

ACB·::i500

DI~K CONTf~Ol.LER

ACB3.530 TAPE

CONTr~OLLEr<

TERMINATOR

FIGURE 5-1. TYPICAL SCSI CONFIGURATION

5.2 SCSI BUS SIGNALS

The SCSI bus contains nine control signals, controlling the bus

phase and all byte transfers, and nine data signals. The

interface is implemented using a 50-pin dual-in-1ine header at

location J3. All odd numbered pins are ground. The suggested

mating connector is 3M PiN 3425-60XX, 3425-70XX or equivalent.

[image:26.617.44.579.37.752.2]

(27)

TABLE

5-1.

SCSI

CONNECTOR, J3,

PIN

ASSIGNMENTS

SIGNAl,

DESCRIPTION

(J,I;

I '

Hi;

t

U

f-

fi

11;,

I~ 1i

; ; ,I

~ ,j ( j I ili(j,··, _Hlf _(I

i:.

3 0 0 4 DB1- Data Bit 1

5 0 0 6 OB2- Data Bit 2

7 o 0 8 DB3- Data Bit 3

9 0 0 10 OB4- Data Bit 4

11 0 0 ₁₂ DB5- Data Bit 5

13

0 0 14

OB6-

Data

Bit

6 15 0 0 16 OB7- Data Bit 7

17 0 0 18 DBP- SCSI Bus Parity Bit

19 0 0 20 GND Ground

21 0 0 22 GNO Ground

~eturn 23 o 0 24 GND Ground

N/c

25 0 0 26 TPWR Bus Terminator Power 27 0 0 28 GND Ground

29 0 0 30 GND Ground

31 o 0 32 ATN- Attention 33 0 0 ₃₄ GND Ground

35 o 0 36 BSY- Busy

37 0 0 38 ACK- Acknowl~dge

39 0 0 40

RST-

Reset

41 0 0 42 MSG- Message

43 0 0

44 SEL-

Select

45 0 0 46 C/O- Control/Data

47 0 0 48

REO-

Request

Return 49 0 0 50 1/0- Input/Output

A description of each signal is as follows:

Busy (BSY-): BSY- is an "or-tied" signal that indicates that the bus i s i n use. Th e A C B ... 3 5 30 A wi 1 l a s s e r t bus y up 0 n be i n 9

selected by an SCSI host.

Select (SEL-): SEL- is an "or-tied signal that is used to select an SCSI device. The SEL- line can be used by a host to select a controller to initiate a command or by a controller to reselect a

host to complete a command (see section 5.3).

Input/Output (1/0-): I/O is driven by the controller to indicate

the direction of information transfers on the SCSI bus relative to the host. Assertion of this signal, In, indicates a

controller-to-host transfer. Out indicates a'host-to-controller trans fer.

[image:27.618.34.593.69.566.2]

(28)

Control/Data (C/D-): C/O- is driven by the controller to

indicate whether a control or data byte is being transferred

across the bus. The type of control information is indicated by

the I/O line. Inbound, controller to INITIATOR, control

information is status. Outbound control information is commands.

I/O also indicates the direction of data transfers.

Message (MSG-): MSG is given by the controller to indicate a

request to send or receive an SCSI message. This signal will be

asserted when the controller desires to send a message, or, in

res po n se to t he h 0 s t as s e r tin 9 A TN - , in die a tin 9 a h 0 s t r e que 5 t

to send a message.

Attention (ATN-): ATN- is driven by the host to indicate a

request to transfer a message to the selected controller.

Request (REQ-): REQ- is driven by the controller to initiate the

REQ/ACK asynchronous handshake of a byte of information to or

from the host. The type of information is indicated by the C/D-,

1/0-, and MSG- signals.

Acknowledge (ACK-): ACK- is driven by the host to complete the

REQ/ACK asynchronous handshake of a byte of information to or from the host.

Data Bits and parity (DBO- to OB7-, DBP-):

eight-bit para llel bus, plus odd parity. significant.

The SCSI contains an

D80- is the least

5.3 SCSI BUS PHASES

The SCSI bus has eight distinct operational phases that are

controlled by the ACB-3530A by the assertion of one or more of:

C/O, I/O, MSG, SEL, and BSY. The eight phases are:

..

Bus Free

•

Command*

4W/ Arbitration

..

Data~

•

Selection

•

Status"

•

Reselection u Message*

*Information transfer phases.

In execution of ~CSI operations, the bus will sequence through a

number of these ~hases. When the bus is between phases, the BSY,

SEL, REO, and ACK signals may not change. The C/O, I/O, MSG and

data lines may change.

(29)

The following sections describe the sequence of events contained within each bus phase, refer to Fiqure 5-2 and Section 5.5 for relative bus timing.

5.3.1 BUS FREE PHASE

The Bus Free phase, indicating that the bus is free and avail~ble

for use is entered by the deassertion and passiv~ release of all

bus signals. At the completion of an SCSI operation, the active

device(s) must deassert all bus signals within 800 ns of release BSY.

SCSI devices sense the Bus Free phase when SEL and BSY are deasserted and the Reset condition is not active.

5.3.2 ARBITRATION PHASE

The Arbitration phase allows one SCSI device to gain control of the bus in systems where more than one device may require the use

o f t he bus. Sy s t ems wit h on e h 0 s tan d S C SId e vice s t hat don 0 t

support reconnection may skip this phase by entering the Selection phase directly from Bus Free.

The sequence of arbitrating for the "bus is as follows:

1. Wait for Bus Free phase: deasserting of both SEL and BSY.

2. After Bus Free is detected, the arbitration device waits a

minimum of 800 ns (bus free delay) to assert BSY and the data bit corresponding to the device's SCSI address ID.

3. The arbitration device then looks on the data bus for an ID

of higher priority. If no higher priority ID's are present,

the device has won control of the bus. If higher priority

ID's exist the device returns to step 1.

4. After winning arbitration, the device asserts SEL and enters

the Selection or Reselection phase.

5.3.3 SELECTION PHASE

The Selection phase allows an INITIATOR (hosi) with control of the bus to select a TARGET (controller) to initiate an SCSI command.

(30)

The sequence for a host to select a controller is as follows:

1. To select a device in nonarbitrating systems, the host asserts the controller 10 address bit and optionally asserts i t ' s own 10.

When selecting a device from the Arbitration phase, the host already has SEL asserted (along with· BSY). The host asserts the controller ID and its own ID and then deasserts BSY.

2. On detecting the simultaneous condition of SEL and its own 10 asserted, and I/O and BSY not asserted, the selected controller examines the data bus for the host ID and responds

by asserting BSY.

3. The host then deasserts SEL and ID address data bits.

5.3.4 RESELECTION PHASE

The Reselection phase is used to re-establish a connection between a host and controller in order to continue a disconnected operation. This phase is entered from the Arbitration phase. Like the Selection phase, the SCSI device with control of the bus has both SEL and BSY asserted. The Reselection phase differs from the Selection phase by the assertion of I/O.

The sequence for a controller to reselect a host is as follows:

1. The controller asserts I/O and the data bits corresponding to its own In address and the desired host IO address. The controller then deasserts BSY.

2. On detecting the simultaneous condition of SEL, I/O and its own ID asserted and BSY not asserted, the reselected host examines the data bus for the controller ID and responds by asserting BSY.

3. After detecting the assertion of BSY, the controller also drives BSY and then releases SEL' and the ID address bits.

4. The host then deasserts BSY leaving the bus in the same state as at the completion of the Selection phase.

5.3.5 INFORMATION TRANSFER PHASE

The Command, Data, Status, and Message phases are used to transfer dat~~or control information across the data bus.

Th e C/O, I/O, and M S G s i 9 n a 1 s are use d to d i f f ere n t i ate the

various information transfer phases~ These signals are not considered valid unless REO is asserted. Table 5-1 shows the bus phases related to the C/O, I/O, and MSG signals.

(31)

TABLE 5-2 •. INFORMATION TRANSFER PHAS'f:S

SIGNAL

DIRECTION OF

MSG C/O I/O PHASE INFORMATION XFER

0 0 0 Data Out Phase Host to ACB-3530A

0 0 1 Data In Phase ACB-3530A to Host

0 1 0 Command Phase Ho~t to ACB-3530A

0 1 1 Status Phase ACB-3530A to Host

1 0 0 - Not Used

1 0 1 - Not Used

1 1 0 Message Out Phase Host to ACB-3530A

1 1 1 Message In Phase ACR-3530A to Host

NOTE:

"l" INDICATES SIGNAL ASSERTION (SCSI BUS SIGNALR ARE NEGATIVE

TRUE) •

The information Transfer Phases use the REO/ACK handshake to

control data transfers. Each REQ/ACK allows the transfer of one

byte of data. The handshake starts with the controller asserting

the REQsignal, requesting a byte transfer. The host responds by

reading or writing a byte of data from/to the bus and as~erts

ACK. The controller then deasserts REO, causing the host to

deassert ACK. See Figure 5-2.

A controller to host data transfer (I/O asserted) occurs with

the ACB-3530A placing data on the bus, assuring i t is valid at

the host interface, and asserting REO. The host then reads the

data and asserts ACK.

A host to controller transfer

(r/o

deasserted) occurs with the

controller asserting REO, requesting a byte of data from the

host. The host places data on the bus, assuring i t is valid at

the controller interface, and asserts ACK.

The BSY signal remains asserted throughout the Information

Transfer Phases.

(32)

CON rROLLEI< l~lQ

h'--

CONIROLLER pr<ESENlS DATA

\

/

0

;-HOST ACK

t_

HOST TAKES DATA

\

0

COf\JTROLLER DATA

---(

>---\

ACB-3530 TO HOSr TRANSFER

CONmOLLER REQ

/

CONrr~OLLER

TAKES

DATA~\

/

0

I

HOST ACK

~

HO~1 pr~bU\jTS

[)AIA

\

0

HOSl DATA

- - - -

-<'---')-~

- - - -

-<----HOST TO ACB-3530 TRANSfER

1 ~. SIGNAL ASSEI<TED o ,-SIGNAL DEASSmT[{)

FIGURE 5-2. REQ/ACK HANDSliAKE

5.3.5.1 COMMAND PHASE

The Command phase is used by the ACB-3530A to obtain Command

Descriptor Blocks (COB) from the host. The sequence for a

command transfer is as follows:

1. A host, in order to execute a command,· arbitrates for the bus

(if arbitrating system) and selects the ACB-3530A.

2. The ACB-3530A becomes selected and places the bus in a

Command phase with REO asserted. _-.,

..

.

'

3.. The command is passed, in a 6-byte block, to the ACB-3530A

using the REQ/ACK handshake and begins execution.

Section 5 .. 6 details the content of a SCSI Command Descriptor Block ..

(33)

5.3.5.2 DATA PHASE

The D~ta phase includes both Data In and Data Out. The Data In

ph a s e i 5 use d by t· he A C B-3 5 30A t o t ran s fer tap e d a tao r con t r 0 1

information (i.e., error codes or configuration data) to the

host. The Data Out phase is used by the host to transfer tape

write data or control information to the ACB-3530A.

The Data phase is typically entered after the Command phase and like command transfers, data is transferred using a RF:Q/ACK handshaking.

5.3.5.3 STATUS PHASE

The Status phase is used by the ACB-3530A to inform thehost of

the state in which the last command completed. The controller

can enter the Status phase at any time to indicate a detected

error. If an error is detected during the six-byte command

transfer, the ACB-3530A will transfer all six bytes and then

enter the status phase. The' controller wi 11 . immediate ly invoke

the Status phase if an error is encountered during a data

transfer. Status information is transferred in single byte from

the controller to host. Section 5.7 details the SCSI status

information.

5.3~5.4 MESSAGE PHASE

The Message phase includes both Message In and Message Out. The

Message In phase is used by the ACB-3530A to transfer acontrol

me s sag e t 0 the h 0 s t (i. e ., pre par e to dis con n e c t ) • Th e Me s sag e

Out phase is used by the hot to transfer a control messg~ to the

controller (i.e., abort operation). In order to enter the

Message Out phase the host must assert the ATN lin'e which causes

the controller to accept the message. Section 5.8 details the

messages supported by the ACB-3530A.

5.3.6 SCSI BUS PHASE SEQUENCING

The execution of commands typically consists of a number of SCSI

bus phases. Figure 5-3 shows a typical sequence of bus phases.

(34)

bUS FREE PHASE

~

ARBITRATION PHASE: HOST ARBITRATES AND GAINS CONTROL

OF BUS.

~

!F· DISCONNECT 1$ SUPPORTED; ATTENTION MESSAGE PHA::'E: HOST SELECTION PHASE: HOST INFORlvlS CONmOLLW OF

SELECTS CONTI<OLLER. • ;\BiLlTY 10 DISCONI'JECI. --ICENTlt=y

~

1

ERROR COMMAND PHASE: HOST _{TiMNSI:ERS 6 BYTE} MESSAGE PHASE: CONmOLLtr<

-... INIOI<MS HOST OF DI:::CONNECIION. COMMAND TO CONTROLLER -·SfWE D/\T/l., POINTEr?S

WITH [<EQ/ACK I-W-lDSHAKE.

----

.- DI$CONN[ CT

~

!

BUS FREE PHASE mr<OR DATA PHASE: DATA

1RANSFEI<RED TO OR FROM

1

THE HOST.

ARBITRAfiON PHASE: CONmOLLm

~

A[~bllr~rtS TO r~fCONI·-.jECT ;'\Nu

Gt,lNS CONTj~OL or Ti it: BUS

l

STATUS PHASE: CONTROLLER

-REPOf<IS STATUS 10 HOST.

RESElECTlON PHASE:

CONlr<OLU:'!~ 1<[CONNEC1S TO HOST

~

_!

MESSAGE PHASE: COMPLETION

._--

MESSAGE PHASE: CONTI<OllEr< MESSAGE DOH TRANSFER1<tD IDENIIFI[S r~f:CONNlCIlNG LuN.

·--IL'[]o,jlifi TO HOST.

-- m::sror,E DATA POINTERS

~

...

"

BUS FREE PHASE

FIGURE 5-3. SCSI BUS PHASE SEQUENCING

(35)

5.4 BUS CONDITIONS

The SCSI bus has two conditions that can interrupt normal phase

sequencinq and initiate certa in device acti vi ty. These are the

Attention and Reset Conditions.

5.4.1 ATTENTION CONDITION

The Attention condition allows the host to signa~ the ACB-3530A

of a waiting message. The ACB-3530A accesses the messaqe by

invoking a Message Out phase and handshaking the message from the

host.

The host may create the Attention condition by asserting ATN at

any time except the Arbitration and Bus Free phase. When the

message byte is to be transferred the host deasserts the ATN signal once the Messaqe Out phase is entered.

The ACB-3530 A may not be abie to respond to the Attention

condition immediately so the host must continue to support the other bus phases while ATN is asserted.

5.4.2 RESET CONDITION AND ABORT MESSAGES

Th e Re set co n d i t ion i sus e d by the h 0 S t toe lea r all de vic e s fro m

the SCSI bus. This condition is created by asserting the RST

si~nal.

Reset can ccc~r at sny ~ime an~ ta~es preced~nce over all ot~er

bus phases and conditions.. On reset, all devices immediately

deassert and passively release all bus signals, thus entering a

Bus Free phase.

Th e R S T s i 9 n a 1 m us t s t a y ass e r ted for a t I e a s t 2 5 uS, w h i 1 e

asserted, no other bus signals can be assumed valid.

The ACB-3530A supports the SCSI "hard" reset mode. Upon reset,

the ACB-3530A releases all bus signals and immediately clears any

commands in process. The ACB-3530A will also rewind the tape to

BOT.

The next command to the ACB-3530A after reset will result in a

ChecK status. The Request Sense

(ISh)

command

will

return a

sense key Unit Attention (6).

The ACB-3530A will respond identically to Abort Messages and SCSI

Reset Messages. The response will be a full reset of the

controller, exactly as an SCSI hardware reset.

5.S

SCSI BUS TIMING

SCSI bus timing is shown in Figure 5-4. The SCSI specification

can provide further timing detail if required.

(36)

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(37)

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FIGURE 5-4. SCSI BUS TIMING (CON'T)