TM 5-6675-320-14
( b ) I n t e r f a c e c l e a r .
I s i n i t i a t e d b y t h e c o m p u t e r . I t c l e a r s t he
l i s t e n , t a l k , p o ll , a n d s e r v i c e r e q u e s t f l i p - f l o p s.
( c ) S e l f - t e s t .
Is used as an aid in locating a defective stage. Self-
test is initiated and controlled by the microprocessor on PCA A3. Self-test for PCA
A2 is accomplished by the microprocessor generating the following test functions:
Test
Test
Test
Test
Test
Test
These functions, when applied in the
PCA A2.
Ready for Data
Data Accepted
Data Available
Data Enable
End or Identify
A t t e n t i o n
appropriate sequence, will test all modes of
Table 4-4, PCA A2 ACCEPTOR HANDSHAKE MODE OPERATION
T h i s f u n c t i o n a l o p e r a t i o n i s d e s i g n e d t o a s s i s t i n t r o u b l e s h o o t i n g t h e p l o t t e r.
All circuit references apply to PCA card A2.
Sequence
Step
Circuit and Signal Operation
INITIATION
1
Computer sends data available (DAV) and attention (ATN) true
s i g n a l s .
2
Control latch U19 generates ready signal indicated by micropro-
cessor upon sensing DAV true signal.
3
Interface bus transceivers (IBT) U33 and U7 receive first data word
from computer and transmit it to bit decode circuits .
4
Interface bus transceiver U34 receives ATN control work from compu-
t e r a n d t r a n s m i t s i t t o b i t d e c o d e c i r c u i t s.
5
U6 receives ATN and READY signals and sets U19.
6
U19 receives ATN and READY signals and sets U8.
7
U8 transmits ready for data (RFD) true from U19 to computer.
Transmits computer response, DAV true signal, to microprocessor
via U22.
DAV goes false.
4-17
