IBM 1 Series Manual page 16

Interrupt Subset
The interrupt subset consists of control buses and tags to support an
interrupting source on the I/O channel. This subset provides the meansto:
(1). present interrupt requests to the processor, (2) resolve contention, (3)
acknowledge an interrupt, and (4) accept an interrupt.
The interrupt subset, in conjunction with the basic subset, supports DPC
devices that are interrupting sources. The I/O signal lines in the interrupt
subset are shown in Figure 2-4.
Service group signal lines
Signal
name Direction
Service gate ———
Service gate return 6
Poll group signal lines
Signal
name Direction
Request in bus 6
Poll identifier SUSE
Poll A
Poll prime sneer
Poll propagate SEs
Poll return fee
Figure 2-4.
Interrupt subset
Number
of lines
1
I
Number
of lines
16
Processor I/O Channel
2-5