IBM 1 Series - Poll Group Line Definitions

Poll Group Line Definitions
Request In Bus. This is a 16-bit inbound bus used by an I/O device to
request an interrupt. Bits 0-15 of the ‘request in bus’ are used by I/O
devices to request interrupts on levels 0-15, respectively. Only levels 0-3
are used on current processors. The level on which the device is to
interrupt corresponds to the encoded value in the level field in the Prepare
command.
Cycle Steal Request In. This is an inbound tag used by a cycle-stealing
device when an access to storage is required.
Poll Identifier. This is a five-bit outbound bus used by the channel to
indicate the nature of the poll presently being propagated to the I/O
devices. ‘Poll identifier’ is always recognizable by I/O devices that are
capable of cycle-stealing and/or presenting interrupts to the processor.
The channel places a value on the poll identifier bus prior to raising the
‘poll’ tag and holds it valid until a ‘poll return’ or ‘burst return’ is received.
The significance of the poll identifier bits is as follows (poll ID bits are
shown using logical representation for active/inactive):
Poll
identifier bits Meaning
0123 4
0
Poll for interrupt level 0
1 Poll for interrupt level 1 -
0 Poll for interrupt level 2
1 Poll for interrupt level 3
0 Poll for interrupt level 4
| Poll for interrupt level 5
0 Poll for interrupt level 6
1 Poll for interrupt level 7
0 Poll for interrupt level 8
1 Poll for interrupt level 9
0 Poll for interrupt level 10
1 Poll for interrupt level 11
0 Poll for interrupt level 12
1 Poll for interrupt level 13
0 Poll for interrupt level 14
1 Poll for interrupt level 15
0 Quiescent value
0
0
0
1
0
1
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Reserved
Reserved
Reserved
Reserved
xX X 1 Reserved
xX X 1 Poll for cycle-steal
The poll identifiers for interrupt levels 4-15 are not used on current
processors.
2-12 GA34-0033