H8SLASH3004 datasheet(77/497 Pages) RENESAS

77 / 497 page

4.2 Reset

4.2.1 Overview

A reset is the highest-priority exception. When the

RES pin goes low, all processing halts and the

H8/3004 and H8/3005 enter the reset state. A reset initializes the internal state of the CPU and the

registers of the on-chip supporting modules. Reset exception handling begins when the

RES pin

changes from low to high.

The H8/3004 or H8/3005 can also be reset by overflow of the watchdog timer. For details see

section 10, Watchdog Timer.

4.2.2 Reset Sequence

The H8/3004 and H8/3005 enters the reset state when the

RES pin goes low.

To ensure that the H8/3004 and H8/3005 are reset, hold the

RES pin low for at least 20 ms at

power-up. To reset the H8/3004 and H8/3005 during operation, hold the

RES pin low for at least

10 system clock (ø) cycles. See appendix D.2, Pin States at Reset, for the states of the pins in the

reset state.

When the

RES pin goes high after being held low for the necessary time, the H8/3004 and

H8/3005 start reset exception handling as follows.

•

The internal state of the CPU and the registers of the on-chip supporting modules are

initialized, and the I bit is set to 1 in CCR.

•

The contents of the reset vector address (H'0000 to H'0003) are read, and program execution

starts from the address indicated in the vector address.

Figure 4-2 shows the reset sequence in modes 1 and 3.

H8/3004 数据表(PDF) 77 Page - Renesas Technology Corp