Control Data Cyber 170 State Hardware Reference Manual page 208

PP Programming
Input/Output Channel Communications
Data t r a n s f e r s t o and from e x t e r n a l d e v i c e s a r e c o n t r o l l e d by PP i n s t r u c t i o n s
64 through 77. The assignment of PPs, t r a n s f e r p r i o r i t i e s , and r e s o l u t i o n of
c o n f l i c t s a r e software r e s p o n s i b i l i t i e s .
Channel p a r i t y and r e s e r v a t i o n must be provided f o r , using t h e channel marker
f l a g a n d l o r software i n t e r l o c k s i n c e n t r a l memory.
A f t e r any c o n f l i c t s have
been r e s o l v e d , proceed a s fbllows:
Action Typical I n s t r u c t i o n
1. Clear t h e e r r o r f l a g . Jump i f t h e e r r o r f l a g i s s e t ,
and c l e a r t h e f l a g (661).
2 . Verify i n a c t i v e s t a t u s . Jump i f a c t i v e (640).
3 .
Verify read s t a t u s :
Prepare f o r reading t h e summary s t a t u s . Function m (771.
Verify t h a t t h e device responded.
Jump i f a c t i v e ( 6 4 0 ) .
A c t i v a t e t h e channel. A c t i v a t e ( 7 4 ) .
Read
t h e summary s t a t u s . Input t o A ( 7 0 ) .
Verify t h e e r r o r f l a g i s c l e a r . Jump i f t h e e r r o r f l a g i s s e t
(661).
Analyze t h e summary s t a t u s .
Logical product ( 1 2 ) . Zero jump
( 0 4 ) .
4.
Enter t h e number of words t o A. Load d ( 1 4 ) .
5. Prepare f o r i n p u t l o u t p u t :
Verify i n a c t i v e s t a t u s .
Prepare f o r r e a d / w r i t e .
Jump i f a c t i v e (640).
Function
m
( 7 7 ) .
Verify t h a t t h e device responded.
Jump
i f
a c t i v e (640).