4570 datasheet(33/69 Pages) RENESAS

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MITSUBISHI MICROCOMPUTERS

4570 Group

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

(4) Return signal

An external wakeup signal is used to return from the RAM

back-up mode because the oscillation is stopped. Table 14

shows the return condition for each return source.

(5) Port P4 control registers

• Key-on wakeup control register K0

Set the contents of this register through register A with

the TK0A instruction. In addition, the TAK0 instruction can

be used to transfer the contents of register K0 to register

• Pull-up control register PU0

transistor. Set the contents of this register through register

A with the TPU0A instruction. In addition, the TAPU0

instruction can be used to transfer the contents of register

PU0 to register A.

Table 14 Return source and return condition

Remarks

Port P0 shares the falling edge detection circuit with ports P1 and P4.

Key-on wakeup functions of ports P0 and P1 are always valid. The key-

on wakeup function valid/invalid of port P4 can be controlled with register

K0. Set the port using the key-on wakeup function selected to “H” level

before going into the RAM back-up mode.

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 mode.

Return condition

Return by an external falling edge

input (“H”

→“L”).

Return by an external “H” level or

“L” level input.

The EXF0 flag is not set.

Return source

Ports P0, P1

and P4

P21/INT pin

4570 Datasheet(PDF) 33 Page - Renesas Technology Corp