Datasheet

Section 4 Exception Handling
Page 98 of 1384 R01UH0310EJ0500 Rev. 5.00
Sep 25, 2012
H8S/2426, H8S/2426R, H8S/2424 Group
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. To ensure that this LSI is reset, hold the RES pin low for at least 15 ms at
power-up. To reset this LSI during operation, hold the RES pin low for at least 2 ms. A reset
initializes the internal state of the CPU and the registers of on-chip peripheral modules. This LSI
can also be reset by overflow of the watchdog timer. For details see section 14, Watchdog Timer
(WDT). 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 time, 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 is cleared to 0 in EXR, and the I bit is set to 1 in EXR and CCR.
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.