TM 5-6675-318-14
PCA A2 TALK HANDSHAKE MODE OPERATION - Cont
Table 3-5.
Sequence
Circuit and Signal Operation
Step
INITIATION - Cont
U9 receives NBA false signal and clears talk handshake flip-flop
17
U17.
18
U 1 5 sets THS true.
DATA TRANSFER
Microprocessor on PCA A3 sends NBA t r u e s i g n a l t o t a l k h a n d s h a k e
1
flip-flop U17.
Computer sends ready for data (RFD) true signal.
2
3
U 2 5 sets data available (DAV) true and enables U15 to generate THS.
4
U2 and U14 transmit data byte from PCA A3 to IBTs U33 and U7.
U 3 3 and U7 are enabled by U27 and transmit data byte to computer.
5
6
M i c r o p r o c e s s o r on PCA A3 sets NBA false, clearing talk handshake
flip-flop U17.
C o m p u t e r generates data accepted (DAC) true.
7
Microprocessor sets DAV false.
8
U15 sets talk handshake (THS) false, thus, indicating completion of
9
transfer.
M i c r o p r o c e s s o r on PCA A3 sends new byte available (NBA) false,
10
causing THS to go false.
Sequence is repeated until all data (data bytes) is transferred.
11
TERMINATION
T e r m i n a t i o n can be initiated by microprocessor on PCA A3 by holding
1
NBA false.
Active termination is initiated by computer when it places an
2
address, other than plotter's preset address, on bits 1-5. This
action will send my address false.
3-21