Specifications

Interrupt Controller (V40)
Specific Priority Rotation
Specific rotation, like automatic rotation, can be used to change the
priorities of the ICU inputs. With automatic rotation, the last request
serviced is rotated into the lowest priority, and other ICU inputs are
rotated up one level. With specific rotation, you specify which
interrupt receives the lowest or highest priority. Either the set priority
command or the rotate on specific FI command can be used to select
this operating mode.
Set Priority
The set priority command is used to define the priority of the ICU
inputs. You specify the lowest priority interrupt as part of the
command. If, for example, you define IRQ4 as part of the set priority
command, then IRQ3 is automatically the second lowest, IRQ2 the
third lowest, and so on up to IRQ5, which is the highest. The
nonspecific FI command must not be used with the set priority
command. This is because the nonspecific FI clears the highest
priority IIS bit, which is not the one most recently serviced if the set
priority command changed priorities. The self finish FI can be used
because it clears the IIS bit during the interrupt acknowledge cycle or,
in other words, before the set priority command can change the
priorities. The specific FI command is the simplest to use because the
level is not selected by the ICU, but specified by you.
Rotate on Specific FI
The rotate on specific FI command is a combination of the set priority
and the specific FI command. The command clears the ISR bit and
changes the priority of interrupt inputs, based on the specified level.
The primary advantage of this command is that it performs the
functions of two commands in one operation.
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