IBM 5-1/4"" Diskette Drive Adapter Hardware Reference Manual

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Personal Computer
Hardware Reference
Library

mM

Drive

6361505

5-1/4" Diskette

Adapter

ii

Contents

Description
Programming Considerations

Digital-Output Register
Floppy Disk Controller
Command Summary
Programming Summary

Interface

System

Drive A and B Interface
Specifications
Logic Diagrams

....................................

.........................

.....................................

I/O

Channel Interface

.................................

................................

......................

......................

.......................

......................

................

.....................

1
3
3
4
8

17

19

19
20
23
25

Hi

iv

Description

The IBM
expansion slots in the system unit.
diskette drives through an internal, daisy-chained flat cable. The
adapter has a connector
rear panel of the system unit. This connector has signals for two

additional external diskette drives; thus, the
drive adapter can attach four
and two external.

The adapter
drives and uses write precompensation with an analog phase-lock
loop for clock and

general-purpose device using the
controller. Therefore, the diskette drive parameters are
programmable. In addition, the attachment supports the diskette

drive's write-protect feature. The adapter

bus and uses the system board's direct memory access (DMA) for
record data transfers.

when an operation

microprocessor attention.

In general, the

high-level command interface to software

5-1/4"

Diskette Drive Adapter fits into one of the

It

is

connected to one or two

at

the other end that extends through the

5-1/4

5-1/4

is

designed for double-density, MFM-coded, diskette

data

recovery. The adapter

An

interrupt level also

is

complete and that a status condition requires

5-1/4

inch diskette drive adapter presents a

inch drives - two internal

NEe

fLPD765

is

I/O

inch diskette

is

a

or equivalent

buffered

is

drivers.

on

used to indicate

the

I/O

Diskette Adapter 1

(l)

......,

>~

<:

ti>-l

(l)

::i. :;J"

Data

Write

AJ"

f---C>

0..0

:;;

..,

......

S·

~(JQ

.

~

...

til

I---

~

"'--

..,

f-----,

<J---

Data

Read
...

....-

0'"

I-----,

5"

()

"-

:;.;"

..-.

0..

>-;

......

..,

8

(JQ

·

~

r'

Enable

Step

Write

Direction

o

......,

.....

Select

Head

Index

(l)

:;J"

Protect

Write

tt:I

-

0

Track

~

VI

On

Motor
A

Drive

I

.j::o.

-

.........

......

ti

(l)

(l)

:;.;"

.....

.....

til

)

Select
A

Drive

""

B

D

f--B

f--C

f--

f--C

r-

r-D

Precompensate

Write
...

Clock

and

r1

t:::'

N

C;"u;,

----

L

1

Circuit

Timing

~

~

('!)

r--.

.

Write

lJata

~

!

Data

Separator

..

DATA

SYNC

STD.

VCO

...

~

Window

I""I"Data

I"'"

NEC

""J../

Disk

Floppy

Controller

--A

hr-v

Buffer

~

V

-V

I"'"

...r.

~

-"<""1

I~

I"'"

I"'"

Decoder

'1

5-1/4 Inch Diskette Drive Adapter Block Diagram

iRes~t

Digital

Control

~

Port

r

J

INTR.

J..-

)

)

~

Programming Considerations

This attachment consists of an 8-bit digital output register in
parallel with a

(FDC).

NEC

JLPD765

or equivalent floppy disk controller

In the following description, drive numbers 0,
equivalent to drives A,

Digital-Output Register

The Digital-Output register (DOR)

B, C, and D.

OJ / ..

is

an

1,

2, and 3 are

output-only register used
to control drive motors, drive selection, and feature enable. All
bits are cleared

by

the

II

0 interface 'reset' line. The bits have the

following functions:
Bits 0 and 1

Bit 2

These bits are decoded
select one drive if its motor

1 0

Bit

00

01

10

1 1

The

FDC

It

must be set by the program to enable the

Drive

o

(A)

1

(B)

2

(C)

3

(D)

is

held reset when this bit

by

the hardware to

is

on:

is

clear.

FDC.

Bit 3

This bit allows the
requests to be gated onto the

If

this bit

request

is

cleared, the interrupt and

I/O

interface drivers are disabled.

FDC

interrupt and

I/O

DMA

interface.

DMA

4,5,6,

Bits

These bits control, respectively, the motors of

and 7 drives 0,

clear, the associated motor
drive cannot be selected.

1,2

(A,

B,

C), and 3 (D).

is

Diskette Adapter 3

If

a bit

off, and the

is

Floppy

The
be accessed
and a data
status information
The

Disk

Controller

floppy disk controller

by

the system unit's microprocessor: a status register

8-bit

register.

data

The

of

the

register (actually consisting

(FDC)

contains two registers

8-bit main status register contains the

FDC

and

may be accessed at any time.

stack with only one register presented
stores data, commands, parameters,
drive

(FDD)
written
after

a particular command.

read

and

system unit's microprocessor

The

bits in

status information.

to

the

data

register in

order

The

is

used to facilitate the transfer

and

the

main status register (hex

and

Data

to

main status register

FDC.

follows:

Bit
Number

DBO
DB1
DB2 FDD C Busy
DB3
DB4
DB5

DB6 Data

DB7 Request

Name
FDD A Busy
FDD B Busy DBB

FDD D Busy
FDC Busy
Non-DMA

Mode

Inputl

Output

for

Master

Symbol

DAB

DCB
DDB
CB
NDM

DIO

ROM

FDD

number
number

FDD
FDD

number

FDD

number 3 is
A read or
The

FDC is in

Indicates
between
then

transfer
the

processor.

is

from

Indicates
receive
bits

DIO and ROM
perform
"ready"

of

several registers in a

to

the

data

bus

at

provides floppy disk

bytes are read from

program

or

obtain results

can

of

data

between

34F)

are defined as

Description

0 is in

the

Seek

mode.

1 is in

the

Seek

mode.

2 is in

the

Seek

mode.

in

the

Seek

mode.

write

the

direction
FDC and

is

the

processor

data

data

to

the

handshaking

and

"direction"

command

from

If

DIO =

register is ready

or

non-DMA

of

data

processor.

FDC

"0;'

to

FDC

from

the

should

is in process.

mode.

transfer

data

then

data

processor.

be used
functions
to

the

that

a time)

or

only
the

If

DIO =

register

transfer
register.

to

send

to

of

processor.

may

be

"1;'

to

or

Both

The

FOe

is

capable of performing

command

is

initiated by a multi-byte transfer from the system

unit's microprocessor,

and

the result after execution of the

15

different commands.

Each

command may also be a multi-byte transfer back to the system

4 Diskette Adapter

unit's microprocessor. Because
information between the
microprocessor, it

consisting of three phases:

is

FDC

convenient to consider each command as

of

this multi-byte interchange of

and the system unit's

,~

Command Phase

The

FDC

receives all information required to perform a particular

operation from the system unit's microprocessor,

Execution Phase

The

FDC

performs the operation it was instructed to do.

Result Phase

After completion of the operation, status and other housekeeping
information are made available to the system unit's
microprocessor ,

The following tables define the symbols used in the command
summary. The command summary immediately follows these
tables,

Diskette Adapter 5

Symbol

AO

C

D

D7-DO Data Bus

DTL

EDT End

GPL

H

HD

HLT

HUT

MF

MT

N

Address

Cylinder

Data

Data Length

of

Length

Gap

Head

Head

Head Load

Head Unload

FM

or

Multi-Track

Number

Name

Line 0

Number

Track

Address

Time

MFM

Mode

Time

controls

AO
register (AO =

C

stands

for

(track)

number

stands

D
to

8-bit
most
least

When
the
read

EDT
a cylinder.

GPL
(spacing
sync

H
specified in

HD
or

HL T
FDD (4

HUT
a read
to

If
high,
is

If
be
and HD1

N
written

for

be

written

data bus,

significant

significant

N is defined as

data

length

from

or

stands

stands

between

field).

stands

for

stands

for

1.

(H

=HD in all

stands

to

512

stands

or

write

480

ms

in

MF

is

low,

MFM

implemented.

MT

performed.

stands

mode

is high, a

will
for

in a sector.

Description

selection

the

the

into a sector.

write

for

for

head

ID

for

for

32-ms

FM

be read

the

of

main

medium.

pattern

that

D7

stands

DO

stands

00,

DTL

sector.

sector

of

gap

excluding

words).
time

increments).

is selected;

only

operation is

under

written.)

of

data

status

0)

or

data register (AO = 1

current/selected

of

the

data

where

bit, and

bit.

that

users are going

to

the

the

final

the

length

sectors

number 0 or

field.

a selected head

command

the

head load

ms

in

4·ms

the

head unload

operation has occurred

increments).

mode

is selected

multi-track

(A

cylinder

or

number

cylinder

is going

for

a

for

stands

to

number

3

1, as

number

in

time

if it

if

MFM

both

bytes

).

a

for

on

VCO

0

the

after

(0

is

to

HDO

Symbol Descriptions (Part 1

6 Diskette Adapter

of

2)

-Symbol Name

NCN

ND

PCN Present

R Record

R/W

SC

SK

SRT

STO
ST 1
ST 2
ST

STP

usa,

US1

3

New

Cylinder

Number

Non-DMA

Cylinder

Number

Read/Write

Sector

Skip

Step

Rate

Status

0

Status

1

Status

2

Status

3

Scan

Test

Unit

Select

Mode

Time

NCN

stands

which

is

the

seek

head.)

stands

stands

at

stands

be read

stands

indicates

stands

stands

stand

the

after

status

0-3

may

been

a scan

in

contiguous

stands

output

going

present

for

to

32

status

should

executed

sectors

the

of
the

ND

mode.

PCN
completion
command
head

R

will

R/W

(W) signal.

SC
cylinder.

SK
mark.

SRT

FDD (2

STO-3
store
command

information
phase

registers

main

ST
has
information
command.

During
data

byte-by-byte

processor
alternate

US
encoded
digital

Description

for a new

operation.

for

for

of

indicating

the

or

for

the

for

skip

for

ms

for

has been

is available during

command

register (selected

be read

relevant

operation,

with

(or

DMAL

for a selected

same as

register (DOR).

cylinder

to

be reached as a

(Desired

operation

cylinder

sense-interrupt-status

time.

written.

either

the

information

in

number

the

position

sector

number,

read

number

one

not

of

deleted-data

stepping

in

2-ms

increments).

of

four

executed.

execution.

be

confused

only

after a command

and

contain

to

that

if

sectors

data

sent

and

if

are read and

drive

bits

0 and 1

the

(R)

STP = 1,

is

number

result

position

non-DMA

at

of

which

or

write

sectors

address

rate

for

registers

after

This

the

with

by

AO =

particular

compared

from

STP = 2,

compared.

number

the

the

per

the

that

a

result

These

the

the

then

of

the

of

the

0).

Symbol Descriptions (Part 2

of

2)

Diskette Adapter 7

Command Summary

In the following table, 0 indicates "logical 0" for that bit, 1 means

1,"

"logical

and X means "don't care."

Phase

Command

R/W

W

D7

MT

D6

MF

Data Bus

D5

D4

Read Data

SK 0 0 1 1 0

W X X X X X HD
W

C

W H
W R
W N
W

EOT

W GPL

Execution

W

Result R ST 0

Command

R
R ST 2
R
R
R R
R

W

MT

MF

DTL

ST 1

C
H

N

Read Deleted Data

SK

0 1 1 0 0

W X X X X X HD
W

C

W H
W R
W N

EOT

GPL
DTL

STO
ST 1

C
H

N

Execution

Result

W
W
W

R
R
R ST 2
R
R
R R
R

D3 D2

D1

DO

US1USO

US1USO

Remarks

Command

Sector

ID

to

command

prior
execution.

Data

transfer

between

and

main

Status

information

after

command
execution.
Sector

ID

after

command
execution.

Command

Sector

ID

prior

to

command

execution.

Data

transfer

between

and

main

Status

information

after

command
execution.

Sector

ID

after

command
execution.

Codes

information

the

FDD

system.

information

Codes

information

the

FDD

system.

information

8 Diskette Adapter

Data

Phase

Command

R/W

07

06

05

W

MT

MF

W

X X X

W
W H
W R
W N
W EOT
W

0 0

W

Execution Data

Result R

R ST 1
R ST 2

R
R H
R
R

Command

W
W

MT

Write

MF

X X X

0 0 1 0 0 1

w

W
W R

W

04

Write

X X

GPL
DTL

STO

Deleted

X X

Bus

03

Data

C

C

R
N

C
H

N

0

Data

02

01

1 0 1

HD US1

HD US1

DO

Command

usa

Sector
prior
execution.

between
system
Status
after
execution.
Sector
after
execution.

Command

usa

Sector
prior
execution.

W EOT
W
W

Execution

Result R

R
R
R
R H
R
R

GPL
DTL

STO
ST 1
ST 2

C

R
N

Data
between
main
Status
after
execution.
Sector

after

execution.

Remarks

Codes

ID

information

to

command

transfer

the

and FDD.

information

command

ID

information

command

Codes

ID

information

to

command

transfer

the

system.

ID

information

command

ID

information

command

main

FDD and

Diskette Adapter 9

Phase

Command

R/W

W 0

W X X X

w

W

W R

W
W

W GPL

Execution

Result

Command

Execution

Result R

W DTL

W 0
W

07

06

05

04

Read

MF

a Track

SK 0

X X HD US1 usa

Oata

C
H prior

N

EOT

R
R
R ST 2
R
R
R
R N

STO
ST 1

C
H
R

Read

MF

0

0

X X X

R ST 1
R ST 2

R
R
R
R

X X

STO

C
H
R

N

Bus

03

02

01

0 0

1 0

10

1 0 1 0

HD US1 usa

00

Remarks

Command

Sector

execution,

Data
between

and main

FDC reads all
cylinder's
from

EOT,

Status

after
execution,

Sector
after
execution,

Command

The

information
cylinder
data register,

Status

after

execution,

Sector

during

phase,

Codes

ID

information

to

command

transfer

the

system,

contents

index hole

information

command

ID

information

command

Codes

first

correct

is

stored

information

command

ID

information

execution

FDD

of

on

to

ID

the

in

10 Diskette Adapter

Phase R/W

Command

W
W X X

w

W
W GPL Gap 3

Execution

Result R

Command

W

R
R
R
R
R
R

W
W X

w

W
W R
W
W
W

Execution

Result R

W

R
R
R
R
R
R

07

06

MF

0

MT

MF

X X X X

Oata

05

0 0

Bus

04

03 02

Format a Track

1 1

X X X

N

SC

D

STO
ST 1
ST 2

C
H

R

N

Scan Equal

SK 1

0 0 0

C
H

N

EOT
GPL
STP

STO
ST 1
ST 2

C
H

R

N

01

0 0

HD

US1

HD US1

00

Remarks

Command Codes

usa

Bytes/Sector
Sector/Track

filler

byte.

FDC

formats
entire cylinder.
Status

information

after

command
execution.
In

this

case,
information
meaning.

1 Command Codes

has no

usa

Sector

10

information

to

command

prior
execution.

Data compared
between
and
Status
after
execution.
Sector
after
execution.

the

the

main

information

Command

ID

information

command

an

the

10

FDD

system.

Diskette Adapter

11

Phase

Command

Execution

Result

Command

Execution

Result

R/W

07

06

W

MT

MT

MF

MF

W X
W
W
W
W
W
W GPL
W STP

R
R

R
R
R

R

R

W
W X

05

Scan

SK

X X

Scan

SK

X X

Data Bus

04
Low

, ,

X X

EOT

STO
ST'

ST 2

High

,

X X

w

W H

W
W
W
W GPL
W STP

R
R
R
R
R
R
R

EOT

STO
ST'

ST 2

03

or Equal

C
H
R

N

C
H
R

N

or Equal

,

C

R

N

C
H
R

N

02

0

HD

,

HD

01

0

US,

0

US,

DO

,

usa

,

usa

execution.

after

Command

execution.

and main
Status

execution.

after
execution.

Remarks

Command

Sector
prior
execution.

Data compared
between
and main
Status
after

Sector

execution.

Sector
prior

Data
between

after

Sector

Codes

ID

information

to

command

the FDD

system.

information

command

ID

information

command

Codes

ID

information

to

command

compared

the

FDD

system.

information

command

ID

information

command

12 Diskette Adapter

Phase R/W

Command W

Execution
No Result
Phase

Command
Result

Command

W

W

R
R

W
W
W

No Result
Phase

Command

W
W

Result

Command

R

W
W
W

Execution

No Result
Phase

Command

Result R

W

07

06

05

0 0

0

X X X

Sense

0 0 0 0

0

0

0 0 0

SRT

r---

0

X 0 X

0 X 0

HLT

Sense Drive

0 0 0 1 0 0

X

0

X

X

Invalid Codes

Data Bus

04

03

Recalibrate

0 0

X 0

X

Interrupt

1

STO

PCN

Specify

Status

X X

ST 3

Seek

1

0

X X

NCN

Invalid

STO

02

01

1 1

US1USO

Status

0 0

1 1

0

HUT--

HDUS1USO

1 1

HDUS1USO

DO

Command

1

Head retracted
track 0

Command Codes

0

Status
the

end
operation
FDC

Command

NO

Command

Status

about

FDD.

Command Codes

1

Head is positioned

over

proper cylinder

on

diskette.

Invalid

codes (NoOp ~ FDC

into

goes
state).

STO=

Remarks

Codes

to

information

of

seek

about

the

Codes

Codes

information

command

standby

80.

at

Diskette Adapter 13

No.

07

06

05

04

03

02

01
00

Bit

Name

Interrupt
Code

Seek End

Equipment
Check

Not

Ready

Head

Address

Unit

Select 1

Unit

Select 0

Symbol Description

IC

SE

EC

NR

HO

US 1

usa

07 = Oand06
Normal
Command

executed.

D7

= 0 and

Abnormal
Execution
was

not

07

= 1 and

command

Invalid

that

was

07

= 1 and

Abnormal
command
from

FOO

When

the

command,
If a fault

or

FOO,
after

77

command),
When

the
and a read or
this

flag is set.
is issued
then

this

This flag is used
the

head

These flags are used
unit

number

= 0

termination

was

termination

of

successfully

issued

termination

execution,

changed
FOC

this

signal is received

if

the

step

FOO

to

flag is set.

at

of

completed

06

= 1

command

06

06

then

side 1

interrupt.

at

completed.

= 0

issue (IC).

was

never

= 1

the

state.

completes

flag is

set

track

0 signal fails

pulses (recalibrate

this

flag is set.

is in

the

write

command

If

a read

of

a single-sided

to

indicate

to

interrupt.

command

of

was

because, during

not-ready

or

indicate a drive

(NT).

and

properly

command

started,

Command

started.

ready signal

the

seek

to

1 (high).

from

the

to

state

is issued,

write

command

the

state

(AT).

but

occur

drive,

of

Command Status Register 0

14

Diskette Adapter

No. Name

End

07

06

D5

D4

D3
D2

01

DO

of

Cylinder

-

Data Error

Over

Run

-

No Data

Not

Writable

Missing
Address
Mark

Bit

Symbol

EN

-

DE

OR

-

ND

NW

MA

When

the

FOC

the

beyond
flag is set.

Not

When

either
flag is set.

If

the
system
certain

Not
During

deleted data,

FDC

the

execution

FDe

error,

execution
command,
found,

During
deleted data. or
command.

write-protect
this

If

the
mark,
time,
the

final

used.

This

the

FDe

the

ID field

FDC is

not

during data

time

interval.

used.

This

execution

cannot

ID register.

data field)

find

of

cannot

read

then

this

of

if

then

this

execution

if

flag is set.

FDe

cannot

this

flag is set. Also.

the

MD

the

or

the read

the

the FDC

(missing address

Description

tries

to

access a

sector

of

bit

is

always

detects a CRe

or

the

serviced

transfers

this

bit

is

always

of

a read

scan

command.

the

sector

this

flag is set. During

ID

the

ID field

flag is set. During the

read a

cylinder

starting

flag is set.

of a write

format-a-cylinder

detects

signal

from

detect

of

status

sector

a cylinder.

0 (low).

error in

data field.

by

the

within

flag

is

set.

0 (low).

data.

specified

command.

without

sector

cannot

data.

a

the

FDO.

the

ID address

at

the

mark

register 2 is set.

this

main

write
if

the

write

then

same

a

if

this

in

the

an

be

in

Command Status Register 1

Diskette Adapter 15

No.
D7

06

D5

04

D3

D2

D1

DO

-

Control

Data Error in
Data Field

Wrong
Cylinder

Scan Equal SH
Hit

Scan
Satisfied

Bad

Missing
Address
in Data Field

Name

Mark

Not

Cylinder

Mark

Bit

Symbol

-

CM During

DO

WC

SN

BC

MD

Description

Not

used. This

command,
that

contains

mark,

this

If

the

FDC

then

this

This

bit

the

contents
different
register,

During
the

condition
flag is set.

During
if

the

FDC
cylinder
this

flag is

This

bit

the

contents

different
register, and
this

flag

When

data is read

the

FDC
or deleted data address mark.
flag is set.

bit

is

always 0 (low).

execution

is related

this

execution

execution

that

is

is

cannot

of

if

flag
detects

flag is set.

from

cannot

set.

related

from

set.

the

the

FDC

a deleted data address

is set.

a CRC error in

to

the

of C on

the

that

stored

flag is

set.

of

the

of

"equal"

of

the

find a sector

meets

the

to

the

of

C on

the

that

stored in

the

contents

from

find

a data address

read data

encounters a sector

ND

bit, and

medium

in

scan

is

satisfied,

scan

condition,

ND bit, and

medium

of

the

medium,

or

the

when

are

the

I D

command,

command,

on

the

then

when

are

the

I D

C is

FF,

mark

then

this

scan

data,

if

this

then

if

Command Status Register 2

16

Diskette Adapter

Bit

No.
D7

D6

D5

D4

D3

D2

D1

DO

Name

Fault

Write
Protected

Ready

Track 0

Two

Side

Head

Address

Unit

Select 1

Unit

Select 0

Symbol

FT

WP

RY

TO

TS

HD

US 1

USO

This bit is
from

This
write-protected

This
from

This
from

This
signal

This
signal

This
signal

This
signal

Command Status Register 3

Programming Summary

the

bit

bit

the

bit

the

bit

from

bit

from

bit

from

bit

from

the

FDD.

is

the

is

the

FDD.

is

the

FDD.

is

the

is

the

is

the

is

the

Description

status

status

signal

status

status

status

the

FDD.

status

the

FDD.

status

the

FDD.

status

the

FDD.

of

of

of

of

of

of

of

of

the

the

from

the

the

the

the

the

the

fault

signal

the

FDD.

ready signal

track

0 signal

two-side

side-select

unit-select-1

unit-select-O

FDC Data Register

Main

FDC
Digital

All bits cleared

Status

Output

Bit 0 Drive

1 Select

2

Not
3 Enable INT &
4 Drive A
5 Drive B
6 Drive C
7 Drive D

OPC Registers

1/0

Address

Register

Register 1/0 Address Hex

FDC Reset

Motor

Motor

Motor
Motor

with

channel reset.

00:
01:

DMA

Enable
Enable
Enable
Enable

1/0

Address

DR
DR

Requests

#A
#B

10:
11:

Hex
Hex

DR
DR

3F5
3F4
3F2

#C
#D

Diskette Adapter 17

FDC Constants (in hex)

N:
SC:

HUT: F HLT: 01

SRT: C

02
08

GPL

Format: 05

GPLR/W:

(6

ms track-to-track)

2A

Drive Constants

Head

Load

Head

Settle

Motor

Start

Comments

•

Head

• Following access, wait HD settle time before

• Drive motors should be off when
Cor

D may run simultaneously. Wait motor start time before ,.,.-..,

R/W.

•

Motor

35 ms

15

ms

250 ms

loads with drive select, wait HD load time before

not

in use. Only A

must be

on

for drive to

be

selected.

R/W.

or

R/W.

Band

Data

•

18

errors can occur while using a home television as the
system display. Placing the
can cause this
away from,

Diskette Adapter

to

occur.

or

to

the opposite side

TV

too close

To

correct the problem, move the

of

to

the diskette area

the system unit.

TV

Interface

System

All signals are TTL-compatible:
Most Positive Up Level + 5.5 Vdc

Least Positive Up Level
Most Positive Down Level
Least Positive

The following lines are used

+DO-7

+AO-9 (Adapter input, Load: 1 74LS): These 10 lines form an

~

+AEN

-lOW

110

(Bidirectional, Load: 1 74LS, Driver: 74LS 3-state):
These eight lines form a bus through which all
commands, status, and data are transferred. Bit 0
the low-order bit.

address bus by which a register
supply the byte transferred through lines DO-7. Bit 0
is the low-order bit.

(Adapter input, load: 1 74LS): The content
A0-9

(Adapter
DO-7 is stored in the register addressed
or

Channel Interface

+2.7Vdc
+0.5

Vdc

Down

DACK2

Level

is ignored if this line is active.

input, Load: 1 74LS): The content

at

the trailing edge

-0.5Vdc

by

this adapter.

is

selected to receive or

of

lines

of

lines

by

lines AO-9

of

this signal.

is

-lOR

-DACK2 (Adapter input, load: 2 74LS): This line being active

(Adapter input, Load: 1 74LS): The content

by

register addressed

onto lines DO-7 when this line

degates

the source

gates T / C

output

or

destination

to

IRQ6.

lines AO-9 or

DRQ2,

selects the

of

bus DO-7, and indirectly

DACK2

is

active.

FDC

data

Diskette Adapter 19

of

the

is gated

register as

+T/C

(Adapter input, load: 4 74LS): This line along with
DACK2 being active indicates that the byte of data for
which the
transferred.

DMA

count was initialized

is

now being

+RESET

+DRQ2

+IRQ6

(Adapter input, load: I 74LS):

operation in process and clears the digital output
register (DOR).

(Adapter output, driver: 74LS 3-state): This line

made active when the attachment

byte of

inactive by DACK2 becoming active or an

the

(Adapter output, driver: 74LS 3-state): This line

made active when the

operation.

should examine the

and determine the ending condition.

data

FDC

data register.

to or from main storage. The line is made

It

results in

FDC

Drive A and B Interface

All signals are TTL-compatible:
Most Positive Up Level

Least Positive Up Level
Most Positive Down Level
Least Positive Down Level

+ 5.5 Vdc

+ 2.4
+ 0.4

- 0.5

An

up level ends any

is

ready to transfer a

I/O

FDC

has completed an

an

interrupt to a routine that

result bytes to reset the line

Vdc
Vdc
Vdc

is

read of

is

All adapter outputs are driven by open-collector gates. The
drives must provide termination networks to Vee (except 'motor
enable', which has a 2,000-ohm resistor to Vee).

is

Each adapter input

20 Diskette Adapter

terminated with a ISO-ohm resistor to Vcc.

Adapter Outputs

~\

r'\

-Drive Select A

-Motor Enable A

-Step

-Direction

and

and

B

B

(Driver: 7438): These two lines are
used by drives A and B to de gate all
drivers to the adapter and receivers
from the attachment (except 'motor
enable') when the line associated
with a drive

is

inactive.

(Driver: 7438): The drive associated

of

with each
its spindle motor such

these lines must control

that

it starts
when the line becomes active and
stops when the line becomes
inactive.

(Driver: 7438): The selected drive

moves the

read/write

head one

cylinder in or out per the direction

on

line for each pulse present

this

line.

(Driver: 7438):

pulse

of

the 'step' line, the
read/write
toward the spindle if this line

For

each recognized

head moves one cylinder

is
active, and away from the spindle if
inactive.

r'\

-Head Select

-Write Data

-Write Enable

(Driver: 7438): Head 1 (upper
head) will be selected when this line
is

active (low).

For

(Driver: 7438):

each

inactive-to-active transition of this

is

line while 'write enable'

active, the

selected drive causes a flux change
to be stored

on

the diskette.

(Driver: 7348): The drive disables
write current in the head unless this

is

line

active.

Diskette Adapter 21

Adapter Inputs

-Index

-Write Protect

-Track 0

-Read Data

The selected drive must supply one pulse per

on

diskette revolution

The selected drive must make this line active
if a write-protected diskette

The selected drive must make this line active

read/write

if the

The selected drive supplies a pulse
line for each flux change encountered
diskette.

this line.

is

in the drive.

head is over track

O.

on

this

on

the

22

Diskette Adapter

Specifications

Note:

Diskette
Drives

lands 1-33
board.
component

At
Ground-Odd

Unused
Index
Motor
Drive
Drive
Motor
Direction
Step
Write
Write
Track 0
Write
Read Data
Select Head 1
Unused

lands 2-34

side.

Standard

Enable A
Select
Select

Enable B

(Stepper

Pulse

Data
Enable

Protect

(odd

TTL

Numbers

B
A

numbers)

(even

Levels

Motor)

34-Pin

Keyed

Edge

Connector

Component

Side

are

on

the

numbers)

are

back

on

Land
1-33

2.4.6
8
10
12
14
16
18
20
22
24
26
28
30
32
34

of

the

the

front.

Number

or

Drive
Adapter

Connector

Specifications

(Part 1

of

2)

Diskette Adapter 23

37-Pin

D-Shell

Connector

o

1 • •

20

At

Standard TTL Levels
Unused
Index

Motor

Enable C
Drive Select D
Drive Select C
Motor

Enable D

Motor)

External
Drives

Direction (Stepper
Step

Pulse

Write

Data

Write

Enable
Track 0
Write

Protect
Read Data
Select Head 1
Ground

Connector Specifications (Part 2

of

2)

19

Pin

Number
1-5
6

7
8

9

10
11
12
13
14
15
16

17

18

20-37

37

o

Drive
Adapter

24

Diskette Adapter

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