HD-15531
Pin Description (Continued)
PIN
NUMBER TYPE
NAME
SECTION
DESCRIPTION
14
15
O
DECODER SHIFT
CLOCK
Decoder Output which delivers a frequency (DECODER CLOCK + 1 2), synchronous by
the recovered serial data stream.
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
17
NC
Blank
Not connected.
O
I
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
19
20
DECODER PARITY
SELECT
Decoder An input for parity sense, calling for even parity with input high and odd parity
with input low.
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.
I
COUNT C0
Both
One of five binary inputs which establish the total bit count to be encoded or de-
coded.
21
22
GROUND
Both
Both
Supply pin.
I
MASTER RESET
A high on this pin clears 2:1 counters in both encoder and decoder, and resets
the ÷ 6 circuit.
23
24
25
I
COUNT C2
Both
See pin 20.
O
O
÷ 6 OUT
Encoder Output from 6:1 divider which is driven by the ENCODER CLOCK.
BIPOLAR ZERO
OUT
Encoder An active low output designed to drive the zero or negative sense of a bipolar
line driver.
26
27
I
OUTPUT INHIBIT
Encoder A low on this pin forces pin 25 and 27 high, the inactive states.
O
BIPOLAR ONE OUT
Encoder An active low output designed to drive the one or positive sense of a bipolar line
driver.
28
29
I
I
SERIAL DATA IN
Encoder Accepts a serial data stream at a data rate equal to ENCODER SHIFT CLOCK.
ENCODER ENABLE
Encoder A high on this pin initiates the encode cycle. (Subject to the preceding cycle be-
ing complete).
30
31
I
I
SYNC SELECT
Encoder Actuates a Command sync for an input high and Data sync for an input low.
Encoder Sets transmit parity odd for a high input, even for a low input.
ENCODER PARITY
SELECT
32
33
34
O
I
SEND DATA
Encoder Is an active high output which enables the external source of serial data.
SEND CLOCK IN
Encoder Clock input at a frequency equal to the data rate X2, usually driven by ÷ 6 output.
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
36
37
NC
Blank
Both
Not connected.
See pin 20.
I
I
COUNT C3
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
40
I
I
COUNT C4
COUNT C1
Both
Both
See pin 20.
See pill 20.
4