Control Data Cyber 170 State Hardware Reference Manual page 53

InputlOutput
Unit
Deadstart
A d e a d s t a r t sequence allows t h e I O U t o i n i t i a l i z e i t s e l f . This d e a d s t a r t
sequence i s i n i t i a t e d by t h e D E A D START switch on t h e system console (CC634
system console uses Control G Control R t o i n i t i a t e t h e d e a d s t a r t sequence).
The d i s p l a y i n c l u d e s c o n t r o l s f o r a s s i g n i n g any P P M t o PPO.
For f u r t h e r
i n f o r m a t i o n , r e f e r t o c h a p t e r 3 .
Barrel and Slot
The b a r r e l c o n s i s t s of t h e R,
A,
P, Q , and
K
r e g i s t e r s , each of which h a s f i v e
ranks ( 0 through 4 ) . Refer t o f i g u r e
2-4.
Information i n t h e s e r e g i s t e r s
moves from one rank t o t h e next a t a uniform 20-MHz r a t e , providing a
multiplexed system of f i v e PPs, each o p e r a t i n g a t a
4-MHz
r a t e .
The r e g i s t e r s
a r e s t a t i o n a r y while t h e PPs r o t a t e . For example, rank 4 r e g i s t e r s c o n t a i n
PPO, PPL, PP2, PP3, and PP4 i n s u c c e s s i o n , each of which consumes 50 n s of t h e
t o t a l c y c l e time of
250
ns.
Each time d a t a e n t e r s t h e s l o t , a p o r t i o n of t h e i n s t r u c t i o n f o r t h a t d a t a i s
executed. The s l o t performs t a s k s such a s a r i t h m e t i c and l o g i c o p e r a t i o n s and
program address manipulation.
Complete execution of an i n s t r u c t i o n may r e q u i r e
t h e R, A, P,
Q ,
and K r e g i s t e r q u a n t i t i e s t o go more than one t r i p around t h e
b a r r e l and through t h e s l o t .
The P P M may be referenced once each time t h e PP passes around t h e b a r r e l and
through t h e s l o t . During i t s s l o t time, t h e PP may a l s o communicate w i t h CM o r
with any of t h e 1 / 0 channels.
PP Registers
The PP r e g i s t e r s , which a r e discussed i n t h e following paragraphs, a r e :
0
R r e g i s t e r .
A
r e g i s t e r .
0
P r e g i s t e r .
0
Q
r e g i s t e r .
0
K r e g i s t e r .