4501 datasheet(160/212 Pages) RENESAS

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2.7 RAM back-up

2-43

4501 Group

APPLICATION

Rev.2.01

Feb 07, 2005

REJ09B0192-0201

Remarks

Key-on wakeup function can be selected with

every one port. Set the port using the key-on

wakeup function to “H” level before going into

the RAM back-up state.

Select the return level (“L” level or “H” level)

with the bit 2 of register I1 according to the

external state before going into the RAM back-

up state.

Return condition

Return by an external “L” level input.

Return by an external “H” level or “L”

level input. The return level can be

selected by register I12. When the

return level is input, the EXF0 flag is

not set.

Table 2.7.2 Return source and return condition

Note: When the bit 3 (K13) of the key-on wakeup control register K1 is “0”, the key-on wakeup (“H” level

or “L” level) of INT pin is set. When the K13 is “1”, the key-on wakeup (“L” level) of port P13 is set.

(2)

Start condition identification

When system returns from both RAM back-up mode and reset, software is started from address 0

in page 0.

The start condition (warm start or cold start) can be identified by examining the state of the power

down flag (P) with the SNZP instruction.

Table 2.7.3 Start condition identification

Fig. 2.7.1 Start condition identified example

Return source

Port P0

Port P1 (Note)

Port P2

Port D2/C

Port D3/K

Port P13/INT

(Note)

Return condition

External wakeup signal input

Reset

P flag

Program start

P = “1”

Yes

Warm start

Cold start

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