RCA 70/46 Reference Manual page 96

Response Procedure
(Cont'd)
Multi-Processor Installation
3. Issues a Program Control instruction to (PI) and sets processor to
non-privileged mode.
4. Changes from (P
2 )
to (PI) and branches to user Read Direct routine.
User Read Direct Routine - (PI) Using the External Interrupt num-
ber, the user Read Direct routine determines the transmitting processor
number and decodes the Data Byte to determine the type of action required.
If the Power Failure code (all zeros) is received, the processor that is
down is removed from the system configuration and a return to normal
processing is effected.
For all other codes received, a Write Direct acknowledgement is issued
as follows:
1. Supervisor Call is issued with a Write Direct Interrupt Code.
2. A Write Direct instruction with a Data Byte of an Acknowledge
Code and a return address of the user Read Direct routine is executed.
When the return is accomplished, the function specified by the Data
Byte initially read is performed, and at the end of the Read Direct process-
ing a branch is made back to the (PI) program.
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