HD6412320 RENESAS [Renesas Technology Corp], HD6412320 Datasheet - Page 134

• Manufacturer Part Number: HD6412320
• Description: Renesas 16-Bit Single-Chip Microcomputer H8S Family H8S-2300 Series
• Manufacturer: RENESAS [Renesas Technology Corp]

Section 4 Exception Handling
4.2
4.2.1
A reset has the highest exception priority.
When the RES pin goes low, all processing halts and the chip enters the reset state. A reset
initializes the internal state of the CPU and the registers of on-chip supporting modules.
Immediately after a reset, interrupt control mode 0 is set.
Reset exception handling begins when the RES pin changes from low to high.
A reset can also be caused by watchdog timer overflow. For details see section 13, Watchdog
Timer.
4.2.2
The chip enters the reset state when the RES pin goes low.
To ensure that the chip 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.
When the RES pin goes high after being held low for the necessary time, the chip starts reset
exception handling as follows:
1. The internal state of the CPU and the registers of the on-chip supporting modules are
2. The reset exception vector address is read and transferred to the PC, and program execution
Figure 4.2 shows an example of the reset sequence.
Rev.6.00 Sep. 27, 2007 Page 104 of 1268
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initialized, the T bit is cleared to 0 in EXR, and the I bit is set to 1 in EXR and CCR.
starts from the address indicated by the PC.
Reset
Overview
Reset Sequence