4

14

O

DECODER SHIFT

CLOCK

Decoder

Output which delivers a frequency (DECODER CLOCK + 1 2), synchronous by

the recovered serial data stream.

15

I

TRANSITION SE-

LECT

Decoder

A high input to this pin causes the transition finder to synchronize on every tran-

sition of input data. A low input causes the transition finder to synchronize only

on mid-bit transitions.

16

NC

Blank

Not connected.

17

O

COMMAND SYNC

Decoder

Output of a high from this pin occurs during output of decoded data which was

preceded by a Command (or Status) synchronizing character.

18

I

DECODER PARITY

SELECT

Decoder

An input for parity sense, calling for even parity with input high and odd parity

with input low.

19

I

DECODER RESET

Decoder

A high input to this pin during a rising edge of DECODER SHIFT CLOCK resets

the decoder bit counting logic to a condition ready for a new word.

20

I

COUNT C0

Both

One of five binary inputs which establish the total bit count to be encoded or de-

coded.

21

GROUND

Both

Supply pin.

22

I

MASTER RESET

Both

A high on this pin clears 2:1 counters in both encoder and decoder, and resets

the

÷ 6 circuit.

23

I

COUNT C2

Both

See pin 20.

24

O

Encoder

Output from 6:1 divider which is driven by the ENCODER CLOCK.

25

O

BIPOLAR ZERO

OUT

Encoder

An active low output designed to drive the zero or negative sense of a bipolar

line driver.

26

I

OUTPUT INHIBIT

Encoder

A low on this pin forces pin 25 and 27 high, the inactive states.

27

O

BIPOLAR ONE OUT

Encoder

An active low output designed to drive the one or positive sense of a bipolar line

driver.

28

I

SERIAL DATA IN

Encoder

Accepts a serial data stream at a data rate equal to ENCODER SHIFT CLOCK.

29

I

ENCODER ENABLE

Encoder

A high on this pin initiates the encode cycle. (Subject to the preceding cycle be-

ing complete).

30

I

SYNC SELECT

Encoder

Actuates a Command sync for an input high and Data sync for an input low.

31

I

ENCODER PARITY

SELECT

Encoder

Sets transmit parity odd for a high input, even for a low input.

32

O

SEND DATA

Encoder

Is an active high output which enables the external source of serial data.

33

I

SEND CLOCK IN

Encoder

Clock input at a frequency equal to the data rate X2, usually driven by

÷ 6 output.

34

O

ENCODER SHIFT

CLOCK

Encoder

Output for shifting data into the Encoder. The Encoder samples SDI pin-28 on

the low-to-high transition of ESC.

35

NC

Blank

Not connected.

36

I

COUNT C3

Both

See pin 20.

37

I

ENCODER CLOCK

Encoder

Input to the 6:1 divider, a frequency equal to 12 times the data rate is usually

input here.

38

O

DATA SYNC

Decoder

Output of a high from this pin occurs during output of decoded data which was

preceded by a data synchronizing character.

39

I

COUNT C4

Both

See pin 20.

40

I

COUNT C1

Both

See pill 20.

PIN

NUMBER

TYPE

NAME

SECTION

DESCRIPTION

HD-15531