Operation Of Hardware Interrupt; Fig. 6.6 Operation Of Hardware Interrupt - Fujitsu MB90420/5 (A) Series Hardware Manual

MB90420/5 (A) SERIES F
n Operation of hardware interrupt
Figure 6.6 shows the operation from the issuance of hardware interrupt to the completion of interrupt
handling.
Internal bus
(7)
2
F MC-16LX CPU
Other resources
Resource that issues the interrupt
request
(8)
IL : Interrupt level setting bit of interrupt control register (ICR)
PS : Processor status
I : Interrupt enable flag
ILM : Interrupt level mask register
IR : Instruction register
FF : Flip-flop
(1) An interrupt factor occurs inside the resource.
(2) When interrupt is enabled after reference of the interrupt enable bit at the resource, an interrupt request
is issued from the resource to the interrupt controller.
(3) After receiving the interrupt request, the interrupt controller determines the priority of interrupts
simultaneously requested and transfers the interrupt level (IL) corresponding to the interrupt request to
the CPU.
(4) The CPU compares the interrupt level requested from the interrupt controller with the value of the
interrupt level mask register (ILM).
(5) As a result of the comparison, when the priority of the interrupt processing level is higher than that of the
current interrupt processing level, the CPU checks the value of the I flag in the condition code register
(CCR).
(6) When result of the check in (5) above shows that the I flag indicates interrupt enable (I = 1), completion
of the currently executing instruction is awaited, and at completion, the requested interrupt level (IL) is set
to ILM.
(7) The registers are saved, and control is branched to the interrupt-processing routine.
(8) Clearance of the interrupt factor generated at (1) by software in the interrupt-processing routine and RETI
instruction terminates the interrupt handling.
2
MC-16LX FAMILY 16-BIT MICROCONTROLLERS HARDWARE MANUAL
PS, PC• •
Microcode
Enable FF
AND
Factor FF
(1)
RAM

Fig. 6.6 Operation of Hardware Interrupt

PS I
IR
Check
(6)
(2)
6-16
ILM
Comparator
(5)
(4)
(3)
Level Interrupt
comparator level IL
Interrupt controller