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Rev. 1.00, 05/04, page 59 of 544
Section 4 Exception Handling
4.1 Exception Handling Types and Priority
As table 4.1 indicates, exception handling may be caused by a reset, interrupt, direct transition, or
trap instruction. Exception handling is prioritized as shown in table 4.1. If two or more exceptions
occur simultaneously, they are accepted and processed in order of priority.
Table 4.1 Exception Types and Priority
Priority Exception Type Start of Exception Handling
Reset Starts immediately after a low-to-high transition of the RES
pin, or when the watchdog timer overflows.
Interrupt Starts when execution of the current instruction or exception
handling ends, if an interrupt request has been issued.
Interrupt detection is not performed on completion of ANDC,
ORC, XORC, or LDC instruction execution, or on
completion of reset exception handling.
High
Direct transition Starts when a direction transition occurs as the result of
SLEEP instruction execution.
Low
Trap instruction Started by execution of a trap (TRAPA) instruction. Trap
instruction exception handling requests are accepted at all
times in program execution state.