HD64F3687GHV Datasheet, PDF (79/566 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 3 Exception Handling
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.
Rev. 3.00 Sep. 10, 2007 Page 45 of 528
REJ09B0216-0300