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User’s Manual U11969EJ3V0UM00
CHAPTER 5 INTERRUPT/EXCEPTION PROCESSING FUNCTION
5.3.3 Priorities of maskable interrupts
The V854 provides multiple interrupt service that accepts an interrupt while servicing another interrupt. Multiple
interrupts can be controlled by priority levels.
There are two types of priority level control: control based on the default priority levels, and control based on the
programmable priority levels that are specified by the interrupt priority level specification bits (xxPRn0 to xxPRn2)
of the interrupt control register (xxICn). When two or more interrupts having the same priority level specified by the
xxPRn0 to xxPRn2 are generated at the same time, the control based on default priority levels services them in the
order of the priority level allocated to each interrupt request type (default priority level) beforehand. For more
information refer to Table 5-1. The programmable priority control customizes interrupt requests into eight levels by
setting the priority level specification flag.
The relation between the programmable priority levels and default priority levels is as follows.
Programmable priority levels > Default priority levels
Note that when an interrupt is acknowledged, the ID flag of PSW is automatically set to “1”. Therefore, when multiple
interrupts are to be used, clear the ID flag to “0” beforehand (for example, by placing the EI instruction into the interrupt
service program) to set the interrupt enable mode.
Remarks xx : Each peripheral unit identifier (OV, CC0, P1, CM1, CM2, CC3, CS, II, SE, SR, ST, AD, P5)
n
: Peripheral unit number (0 to 4)
Содержание V854 UPD703006
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