TM 5-6675-320-14
Table 4-5. PCA A2 TALK HANDSHAKE MODE OPERATION - Cont
Sequence
Step
Circuit and Signal Operation
17
18
1
2
3
4
5
6
7
8
9
10
11
1
2
INITIATION - Cont
U9 receives NBA false signal and clears talk handshake flip-flop
U17.
U15 sets THS true.
DATA TRANSFER
Microprocessor on PCA A3 sends NBA true signal to talk handshake
f l i p - f l o p U 1 7 .
Computer sends ready for data (RFD) true signal.
U25 sets data available (DAV) true and enables U15 to generate THS.
U2 and U14 transmit data byte from PCA A3 to IBTs U33 and U7.
U33 and U7 are enabled by U27 and transmit data byte to computer.
Microprocessor on PCA A3 sets NBA false, clearing talk handshake
f l i p - f l o p U 1 7 .
Computer generates data accepted (DAC) true.
Microprocessor sets DAV false.
U15 sets talk handshake (THS) false,
t h u s , i n d i c a t i n g c o m p l e t i o n o f
t r a n s f e r .
Microprocessor on PCA A3 sends new byte available (NBA) false,
causing THS to go false.
Sequence is repeated until all data (data bytes) is transferred.
TERMINATION
Termination can be initiated by microprocessor on PCA A3 by holding
NBA false.
Active termination is initiated by computer when it places an
address, other than plotter’s preset address, on bits 1-5. This
action will send my address false.
4-21
