SH7136 datasheet(105/1160 Pages) RENESAS

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Section 5 Exception Handling

Rev. 2.00 Sep. 10, 2008 Page 79 of 1130

REJ09B0402-0200

5.2

Resets

5.2.1

Types of Resets

Resets have priority over any exception source. There are two types of resets: power-on resets and

manual resets. As table 5.5 shows, both types of resets initialize the internal status of the CPU. In

power-on resets, all registers of the on-chip peripheral modules are initialized; in manual resets,

they are not.

Table 5.5

Reset Status

Conditions for Transition to

Reset State

Internal State

Type

RES

WDT

Overflow

MRES

CPU, INTC

On-Chip

Peripheral

Module

POE, PFC,

I/O Port

Low



Initialized

Power-on reset

High

Overflow

High

Initialized

Manual reset

High

Not overflowed Low

Initialized

Not initialized Not initialized

5.2.2

Power-On Reset

Power-On Reset by

RES Pin: When the RES pin is driven low, this LSI enters the power-on

reset state. To reliably reset this LSI, the

RES pin should be kept low for at least the oscillation

settling time when applying the power or when in standby mode (when the clock is halted) or at

least 20 tcyc when the clock is operating. During the power-on reset state, CPU internal states and

all registers of on-chip peripheral modules are initialized. See appendix A, Pin States, for the

status of individual pins during power-on reset mode.

In the power-on reset state, power-on reset exception handling starts when driving the

RES pin

high after driving the pin low for the given time. The CPU operates as follows:

1. The initial value (execution start address) of the program counter (PC) is fetched from the

exception handling vector table.

2. The initial value of the stack pointer (SP) is fetched from the exception handling vector table.

3. The vector base register (VBR) is cleared to H'00000000 and the interrupt mask bits (I3 to I0)

of the status register (SR) are set to H'F (B'1111).

4. The values fetched from the exception handling vector table are set in PC and SP, then the

program starts.

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