IBM Series 1 User Manual page 192

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Interrupt Se£vic~ Seguence
Figure 6-4 is a
service sequence.
timing diagram for a typical interrupt
This sequence is executed as follows:
1. The device address bits are placed on their appropriate
lines.
2. The interrupt service active tag is skewed (at least
200
nanoseconds) and activated on the interface.
3. Upon recognition of address compare and interrupt
service active, the device raises the select response
tag. Once raised, this tag must be held active at
least until the fall of the interrupt service active
tag. Condition code in and data bus in must be active
for the duration of the select response tag or at least
remain active until strobe becomes active.
4.
Strobe is activated and dropped.
The I/O device must
reset its interrupt request at the leading edge of the
strobe.
S. The
interrupt service active tag is deactivated.
6. Upon recognition of the absence of the interrupt
service active tag, the device drops select response,
condition code in, and data bus in.
7.
The device address is deactivated.
Figure
6-4.
Interrupt service sequence timing diagram
Device
address
bits
Interrupt
service
active
Strobe (device)
Select response
Condition code in
and data bus in
Interrupt service sequence
Strobe
L - - - T - -
>200 ns
customer DPC Adapter 6-11