Fujitsu F2MC-16LX Hardware Manual page 370

CHAPTER 18 DTP/EXTERNAL INTERRUPT UNIT
I External interrupt request level
• If edge input has been selected for the request input level, at least a pulse width of three
machine cycles is required for detecting requests.
• If level input has been selected for the request input level, note that an external request that
has been input remains active with respect to the interrupt controller even if it is no longer
being input, since the interrupt controller contains an internal source retention circuit. To
withdraw a request with respect to the interrupt controller, the source retention circuit must
be cleared.
Figure 18.4-1 Clearing the source retention circuit when setting the request level
Interrupt
Level detection
source
Figure 18.4-2 Interrupt sources and requests to the interrupt controller when interrupts are enabled
Interrupt source
Interrupt request to
interrupt controller
Note:
Edge detection cannot be used to return from watch mode.
354
Source F/F
(source retention
circuit)
Source is retained
until cleared
H level
Turned to inactive by clearing source F/F
To interrupt
Enable gate
controller