Control Data Cyber 170 State Hardware Reference Manual page 212

PP Programming
Channel (Marker) Flag lnstructions (641, 651)
Software uses t h i s f l a g software a s a marker.
This f l a g does not a f f e c t
hardware operation. When PPs i n t h e same time s l o t use t h i s f l a g , p r i o r i t y
.
c o n f l i c t s e x i s t . For channel (maintenance channel) marker f l a g , hardware
r e s o l v e s p r i o r i t y problems. For o t h e r channels, software must r e s o l v e such
c o n f l i c t s .
Any
f i v e consecutively numbered PPs a r e not i n t h e same time s l o t .
Error Flag lnstructions (661, 671)
This f l a g i n d i c a t e s an i n p u t d a t a p a r i t y e r r o r on t h e s p e c i f i c channel being
t e s t e d .
The f l a g a l s o i n d i c a t e s an output d a t a p a r i t y e r r o r on channels t h a t
have t h e c a p a b i l i t y of sending an e r r o r s i g n a l t o t h e I O U i n c a s e
o f such an
e r r o r . The s t a t u s r e g i s t e r of t h e device concerned must be read t o v e r i f y
output d a t a i n t e g r i t y .
Channel Transfer Timing
Figure 5-7 shows channel t r a n s f e r timing.
A l l s i g n a l p u l s e s a r e 25 +5 n s i n -
width and occur
25
2 5 n s following t h e 10-MHz clock.
To maintain t h e f a s t e s t p o s s i b l e c y c l e time (500 u s ) , a f u n c t i o n / f u l l / e m p t y
pulse from t h e PP must be answered w i t h a n i n a c t i v e / e m p t y / f u l l p u l s e ,
r e s p e c t i v e l y , w i t h i n 310
235
ns.
I f t h e maximum speed
i s
n o t r e q u i r e d , t h i s
response time may be increased by m u l t i p l e s of 100 ns.
The PP master clock frequency
can be v a r i e d by 2 2 percent. The p e r i p h e r a l
devices used must t o l e r a t e t h i s ' frequency v a r i a t i o n .