Control Data Cyber 170 State Hardware Reference Manual page 216

PP Programming
Data Output Sequence
The PP send . a t a ( f i g u r e 5-91 t o the e x t e r n a l device
as follows.
The PP p l a c e s a f u n c t i o n word i n t h e channel r e g i s t e r and s e t s the f u l l
f l a g and t h e channel a c t i v e f l a g . The function s i g n a l causes a l l
c o n t r o l l e r s t o sample t h e word and i d e n t i f y t h e word as a f u n c t i o n code
r a t h e r t h a n a d a t a word. Connect codes s e l e c t c o n t r o l l e r s and modes of
operation and c l e a r nonselected c o n t r o l l e r s .
Only s e l e c t e d c o n t r o l l e r s a r e
connected.
The c o n t r o l l e r s e n d s , a n i n a c t i v e s i g n a l t o t h e PP, i n d i c a t i n g acceptance of
the f u n c t i o n code. The s i g n a l drops t h e channel a c t i v e f l a g , which i n
t u r n , drops the f u l l f l a g and c l e a r s the channel r e g i s t e r .
The PP s e t s the channel a c t i v e f l a g and sends a n a c t i v e s i g n a l t o t h e
c o n t r o l l e r , which s i g n a l s the output equipment t h a t d a t a flow
i s
s t a r t i n g .
The PP p l a c e s a 12-bit d a t a word p l u s 1 p a r i t y b i t i n t h e channel r e g i s t e r
and s e t s t h e f u l l f l a g . Coincidently, t h e PP sends
a
word w i t h p a r i t y
and
a f u l l s i g n a l t o the c o n t r o l l e r .
The c o n t r o l l e r a c c e p t s t h e word and sends an empty s i g n a l t o t h e PP where
t h e s i g n a l c l e a r s t h e channel r e g i s t e r and drops t h e f u l l f l a g .
Steps
4
and
5
r e p e a t f o r each PP word.
A f t e r t h e l a s t word
is
t r a n s f e r r e d and acknowledged by t h e c o n t r o l l e r empty
s i g n a l , t h e PP drops t h e channel a c t i v e f l a g and t u r n s off t h e c o n t r o l l e r
with an i n a c t i v e s i g n a l .