TM 5-6675-323-14
Table 3-4. PCA A2 ACCEPTOR HANDSHAKE MODE OPERATION - Cont
Sequence
Circuit and Signal Operation
Step
TRANSFER OF DATA - Cont
Computer sends DAV false.
6
7
U6, U27, and U19 set DAC false and RFD true.
8
Process is repeated until all data to be transferred from computer
is transferred.
TERMINATION
1
Computer initiates termination by placing a 11111 bit on data bits
1-5.
U 1 6 , U4, and U26 decode bits 1-5 and input CLK false to U17A.
2
3
U 1 7 A is clocked by decoded bits 6 and 7 and sets listen (LST)
signal to false.
L S T signal to U19 is removed and U10 stops generating receive
4
h a n d s h a k e (RHS) signal.
5
P l o t t e r has exited RHS mode.
Table 3-5. PCA A2 TALK HANDSHAKE MODE OPERATION
Sequence
Circuit and Signal Operation
Step
INITIATION
Interface bus transceivers U33 and U7 receive first data word from
1
computer and transmit it to bit decode circuits.
U 4 and U5 receive and decode bits 6 and 7 from U33. A BIT 7 true
2
a n d BIT 6 false decodes a talk handshake (THS) mode and a talk
decode clock pulse is sent to talk flip-flop U18B.
3
A d d r e s s comparator U20 compares bits 1-5 from computer to the five
b i t s from preset ADDRESS switch S1 on PCA A1. If bits are same,
U20 generates my address indicating that plotter is being
addressed.
3-19
