Rev. 1.0, 09/02, page 55 of 568
4.3 Reset
A reset has the highest exception priority.
When the
RES
pin goes low, all processing halts and this LSI enters the reset state. To ensure that
this LSI is reset, hold the
RES
pin low for at least 20 ms at power-up. To reset the chip during
operation, hold the
RES
pin low for at least 20 states. A reset initializes the internal state of the
CPU and the registers of on-chip peripheral modules.
The chip can also be reset by overflow of the watchdog timer. For details, see section 13,
Watchdog Timer.
The interrupt control mode is 0 immediately after reset.
4.3.1
Reset Exception Handling
When the
RES
pin goes high after being held low for the necessary period, this LSI starts reset
exception handling as follows:
1. The internal state of the CPU and the registers of the on-chip peripheral modules are
initialized, the T bit in EXR is cleared to 0, and the I bit in EXR and CCR is set to 1.
2.
The reset exception handling vector address is read and transferred to the PC, and program
execution starts from the address indicated by the PC.
Figures 4.1 and 4.2 show examples of the reset sequence.
Содержание H8S/2627
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