Datasheet

Section 4 Exception Handling
Rev.7.00 Dec. 24, 2008 Page 81 of 698
REJ09B0074-0700
Section 4 Exception Handling
4.1 Exception Handling Types and Priority
As table 4.1 indicates, exception handling may be caused by a reset, trace, trap instruction, or
interrupt. 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. Exception sources, the stack
structure, and operation of the CPU vary depending on the interrupt control mode. For details on
the interrupt control mode, refer to section 5, Interrupt Controller.
Table 4.1 Exception Types and Priority
Priority Exception Type Start of Exception Handling
High Reset Starts immediately after a low-to-high transition at the RES or
MRES* pin, or when the watchdog timer overflows. The CPU
enters the reset state when the RES pin is low. The CPU enters
the manual reset state when the MRES pin* is low.
Trace Starts when execution of the current instruction or exception
handling ends, if the trace (T) bit in the EXR is set to 1. This is
enabled only in trace interrupt control mode 2. Trace exception
processing is not performed after RTE instruction execution.
Interrupt Starts when execution of the current instruction or exception
handling ends, if an interrupt request has been issued. Note that
after executing the ANDC, ORC, XORC, or LDC instruction or at
the completion of reset exception processing, no interrupt is
detected.
Low Trap instruction
(TRAPA)
Started by execution of a trap instruction (TRAPA). Trap exception
processing is always accepted in program execution state.
Note: * Supported only by the H8S/2218 Group.
4.2 Exception Sources and Exception Vector Table
Different vector addresses are assigned to different exception sources. Table 4.2 lists the exception
sources and their vector addresses. Since the usable modes differ depending on the product, for
details on each product, refer to section 3, MCU Operating Modes.