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User’s Manual U15017EJ2V0UD
CHAPTER 16 INTERRUPT FUNCTION
The
μ
PD784975A is provided with the following three interrupt request service modes: vectored interrupt, context
switching, and macro service modes (refer to
Table 16-1
). These three service modes can be set as required in the
program. However interrupt service by macro service can only be selected for interrupt request sources provided
with the macro service processing mode shown in Table 16-2. Context switching cannot be selected for non-maskable
interrupts or operand error interrupts.
Multiple interrupt control using 4 priority levels can easily be performed for maskable vectored interrupts.
Table 16-1. Interrupt Request Service Modes
Interrupt Request
Service Mode
Servicing Performed
PC & PSW Contents
Service
Vectored interrupts
Software
Saving to & restoration
from stack
Executed by branching to service program
at address
Note
specified by vector table
Context switching
Saving to & restoration
from fixed area in
register bank
Executed by automatic switching to
register bank specified by vector table
to service program at address
Note
specified by and branching fixed area in
register bank
Macro service
Hardware
(firmware)
Retained
Execution of pre-set service such as data
transfers between memory and I/O
Note
The start addresses of all interrupt service programs must be in the base area. If the body of a service
program cannot be located in the base area, a branch instruction to the service program should be written
in the base area.