H8SX1663 datasheet(132/1158 Pages) RENESAS

132 / 1158 page

Section 4 Exception Handling

Rev.1.00 Jun. 07, 2006 Page 80 of 1102

REJ09B0294-0100

Table 4.3

Calculation Method of Exception Handling Vector Table Address

Exception Source

Calculation Method of Vector Table Address

Reset, CPU address error

Vector table address = (vector table address offset)

Other than above

Vector table address = VBR

+ (vector table address offset)

[Legend]

VBR: Vector base register

Vector table address offset: See table 4.2.

4.3

Reset

A reset has priority over any other exception. 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 with the

STBY pin driven high when the power is turned on. When operation is in progress,

hold the

RES pin low for at least 20 cycles.

The chip can also be reset by overflow of the watchdog timer. For details, see section 14,

Watchdog Timer (WDT).

A reset initializes the internal state of the CPU and the registers of the on-chip peripheral modules.

The interrupt control mode is 0 immediately after a 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, VBR is cleared to H'00000000, the T bit is cleared to 0 in EXR, and the I bits are

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.

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