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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.