Pin Designations
Pin Input Output Enc Dec
Function
Comment
1
2
3
4
5
6
7
8
9
10
11
12
–
Valid word
A 'high' signals the receipt of a valid word
Encoder Shift Clock
Shifts data into the encoder on a 'low' to 'high'
transition
Take Data
'high' during data reception after the sync pulse is
identified
Serial Data Out
NRZ output of received data
Decoder clock
Clock for the transition finder and synchronizer which
generates the clock for the rest of the decoder
Bipolar Zero In
Should be 'high' when the bus is in a negative state.
Must be tied 'high' when the unipolar input is used
Bipolar One In
Should be 'high' when the bus is in a positive state.
Must be tied 'low' when the unipolar input is used
Unipolar Data In
Input for unipolar data to the transition finder. Must be
tied 'low' when not used
Decoder Shift Clock Provides the DECODER CLOCK divided by 12,
synchronized by the recovered serial data
Command/Data Sync This output indicates the type of synchronizing
character received as follows: If a data synchronizing
character was received, this pin is low while the data
is decoded. If a command synchronizing character
was received, this pin is high during data decoding
Decoder Reset
A 'high' during a DECODER SHIFT CLOCK rising
edge resets the bit counter
–
VSS
Ground
13
14
15
16
17
18
19
20
21
22
Master Reset
A 'high" clears the counters in both sections
÷ 6 Out
Provides the ENCODER CLOCK divided by 6
Bipolar Zero Out
Provides an active 'low' output to the zero or negative
sense of a bipolar line driver
Output Inhibit
A 'low' inhibits the BIPOLAR ZERO OUT and
BIPOLAR ONE OUT by forcing them to inactive, 'high',
states
Bipolar One Out
Provides an active 'low' output to the one or positive
sense of a bipolar line driver
Serial Data In
Receives serial data at the rate of the ENCODER
SHIFT CLOCK
Encoder Enable
A 'high' starts the encode cycle provided that the
previous cycle is complete
Sync Select
A 'high' selects the command sync and a 'low' selects
the data sync
Send Data
Provides an active 'high' to enable the external serial
data source
Send Clock In
Clock input at 2 times the data rate
23
Encoder Clock
Input to the divide by 6 circuit
24
–
–
VDD
Positive Supply
Aeroflex Circuit Technology
Figure 4: Pin Designations (24-Pin Dip/FlatPack)
3
SCD15530 REV B 7/28/99 Plainview NY (516) 694-6700