Datasheet

Section 3 Exception Handling
Rev. 3.00 Mar. 15, 2006 Page 43 of 526
REJ09B0060-0300
Section 3 Exception Handling
Exception handling may be caused by a reset, a trap instruction (TRAPA), or interrupts.
• Reset
A reset has the highest exception priority. Exception handling starts as soon as the reset is cleared
by the RES pin. The chip is also reset when the watchdog timer overflows, and exception handling
starts. Exception handling is the same as exception handling by the RES pin.
• Trap Instruction
Exception handling starts when a trap instruction (TRAPA) is executed. The TRAPA instruction
generates a vector address corresponding to a vector number from 0 to 3, as specified in the
instruction code. Exception handling can be executed at all times in the program execution state,
regardless of the setting of the I bit in CCR.
• Interrupts
External interrupts other than NMI and internal interrupts other than address break are masked by
the I bit in CCR, and kept masked while the I bit is set to 1. Exception handling starts when the
current instruction or exception handling ends, if an interrupt request has been issued.