Operation - Fujitsu MB91460 SERIES FR60 User Manual

Chapter 24 Interrupt Control

5.Operation

5. Operation
The following section explains priority determination operation of interrupt control.
The Flow of the Interrupt Process
NO
Priority determination
Interrupt control circuit
Is not the corresponding interrupt disabled?
Interrupt level = 31
Interrupt number
= indeterminate
The interrupt level and the interrupt number
■ Priority determination
• The interrupt control circuit selects the highest priority factor from those that have been generated
simultaneously, and outputs the factor's interrupt level (ICR) and interrupt number (#) to the CPU.
• The priority level criteria of an interrupt cause are the following conditions.
• The value of the interrupt level is not 31. (31 is "interrupt disable")
• The factors with the smallest interrupt level.
• Among these, the factor that has the smallest interrupt number.
• If nothing is applicable by the above-mentioned criteria, interrupt level 31 (11111
case, the interrupt number is indeterminate.
318
Interrupt cause generated
The interrupt request flag is set to "1".
Are interrupt requests enabled?
YES
The interrupt request is transmitted to
the interrupt control circuit.
(ICR) < 31?
YES
Which interrupt has the lowest level
among the interrupt requests?
The lowest interrupts
Which interrupt has the lowest
number (#) among the lowest
interrupt requests?
The interrupt with
the lowest number
are transmitted to the CPU.
CPU processing
Is the interrupt level higher than
the interrupt mask level?
(ICR) < (ILM)
YES
Are interrupts enabled?
I flag = 1
YES
Wait until the executed instructions finish
Transition processing to interrupts
- Save to the system stack (PS and PC)
- Set an interrupt level to ILM
- System stack enabled
- Branch to the interrupt routine
(PC <= interrupt vector)
NO
NO
) is sent to the CPU. In this
B