143

Block Diagrams

ENCODER

DECODER

GND

MASTER RESET

SEND CLK IN

BIT

COUNTER

CHARACTER

12

13

22

14

ENCODER

CLK

23

FORMER

21

2

18

19

20

15

17

SEND

DATA

SERIAL

DATA IN

ENCODER

ENABLE

SYNC

SELECT

ENCODER

16

BIPOLAR

ONE OUT

BIPOLAR

ZERO OUT

24

OUTPUT

INHIBIT

SHIFT CLK

7

6

UNIPOLAR

DATA IN

BIPOLAR

ONE IN

BIPOLAR

ZERO IN

DECODER

CLK

MASTER

RESET

8

TRANSITION

FINDER

SYNCHRONIZER

5

13

DECODER

RESET

11

BIT

COUNTER

BIT

RATE

CLK

PARITY

CHECK

9

1

DECODER

SHIFT

CLK

CHARACTER

IDENTIFIER

10

3

VALID

WORD

SERIAL

DATA OUT

COMMAND/

DATA SYNC

TAKE

DATA

4

Pin Description

PIN

NUMBER

TYPE

NAME

SECTION

DESCRIPTION

1

O

VALID WORD

Decoder

Output high indicates receipt of a valid word, (valid parity and no Manches-

ter errors).

2

O

ENCODER SHIFT

CLOCK

Encoder

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

low-to-high transition of Encoder Shift Clock.

3

O

TAKE DATA

Decoder

Output is high during receipt of data after identification of a sync pulse and

two valid Manchester data bits.

4

O

SERIAL DATA OUT

Decoder

Delivers received data in correct NRZ format.

5

I

DECODER CLOCK

Decoder

Input drives the transition finder, and the synchronizer which in turn

supplies the clock to the balance of the decoder, input a frequency equal to

12X the data rate.

6

I

BIPOLAR ZERO IN

Decoder

A high input should be applied when the bus is in its negative state. This pin

must be held high when the Unipolar input is used.

7

I

BIPOLAR ONE IN

Decoder

A high input should be applied when the bus is in its positive state. This pin

must be held low when the Unipolar input is used.

8

I

UNLPOLAR DATA IN

Decoder

With pin 6 high and pin 7 low, this pin enters unipolar data into the transition

finder circuit. If not used this input must be held low.

9

O

DECODER SHIFT

CLOCK

Decoder

Output which delivers a frequency (DECODER CLOCK

nized by the recovered serial data stream.

10

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. A low

output indicates a Data synchronizing character.

11

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.

12

I

GROUND

Both

Ground Supply pin.

13

I

MASTER RESET

Both

A high on this pin clears 2:1 counters in both Encoder and Decoder, and

resets the

14

O

Encoder

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

15

O

BIPOLAR ZERO OUT

Encoder

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

bipolar line driver.

16

I

OUTPUT INHIBIT

Encoder

A low on this pin forces pin 15 and 17 high, the inactive states.

17

O

BIPOLAR ONE OUT

Encoder

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

line driver.

HD-15530