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System Service
CTL DATA BUS
f
1
f
PORT CONTROLLER
CPU
lOP
MEMORY
CHAN
I
CHAN
I
CHAN
I
CHAN
1
2
3
4
•
,1.
lOP BUS
.~
MAINTENANCE PCA
'
..
,
STATUS
)
f
r
COMPAR-
I
.--..
ATOR
....
,
CNTR BUFFER
BUS
.,.
.,.
LOGIC
LOAD
INC
ROLL
OVER
I.
~:
CONTROL LOGIC
, ... NO COMPARE
)
,
CONTROL REG
...
,
.~
,1.
SEL CHAN BUS
Figure 4-2. SCMB Block Diagram
4-15.
I/O INSTRUCTIONS. The following is a list of applicable I/O instructions and their effect
upon the SCMB.
a. SIN Instruction -
Sets the SCMB interrupt request flip-flop.
b.
CIa Instruction - Loads a control word from the TOS into the SCMB control register.
c.
SIO Instruction - Initiates I/O program execution if the channel is inactive. The SIO instruction
is rejected if the channel is currently active.
d. WIO Instruction -
Loads a data word from the TOS into the counter/buffer.
e.
RIO Instruction - Sends the contents of the counter/buffer to the TOS.
f.
TIO Instruction -
Returns the SCMB status word to the TOS.
g. SMSK Instruction - This instruction is ignored because the SCMB has no mask flip-flop.
4-8
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