Control Data Cyber 170 State Hardware Reference Manual page 237

Maintenance Channel Programming
MCH
Programming for Master Clear/Clear Errors (Opcode
6/7)
These operations c o n s i s t of t h e output of a s i n g l e f u n c t i o n word. The master
c l e a r immediately and a r b i t r a r i l y c l e a r s the connected u n i t without regard to
p o s s i b l e information l o s s .
Clear e r r o r s c l e a r s the e r r o r i n d i c a t o r s
i n
t h e
connected u n i t . To avoid l o s s of e r r o r information while the e r r o r s a r e
c l e a r e d , t h e u n i t concerned should be h a l t e d .
MCH Echo (Opcode 8)
This operation checks the d a t a path between the MCH and t h e I O U MAC.
Following
t h e o p e r a t i o n MCH
i s
a c t i v a t e d and
2
bytes a r e s e n t t o I O U MAC. I O U i g n o r e s
t h e f i r s t byte and l a t c h e s t h e second byte i n t h e Address Holding R e g i s t e r i n
any d a t a p a t t e r n .
MCH i s d e a c t i v a t e d after the second byte i s accepted i n I O U
MAC, and t h e channel i s a c t i v a t e d followed by an input sequence. I O U MAC sends
d a t a ( c o n t e n t s of Address Holding R e g i s t e r ) upon r e c e i v i n g t h e Active s i g n a l
and subsequent Empty s i g n a l s . There i s no r e s t r i c t i o n on t h e number of
data
words read.
MCH Programming for Read IOU Status summary (Opcode
C, IOU Only)
This o p e r a t i o n i s an a l t e r n a t i v e , f a s t e r means of reading t h e I O U s t a t u s
summary r e g i s t e r .
1.
I s s u e function with opcode C.
2. Input s t a t u s summary byte.