4570 Datasheet, PDF (33/69 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

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
Register K0 controls the port P4 key-on wakeup function.
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
A.
• Pull-up control register PU0
Register PU0 controls the ON/OFF of the port P4 pull-up
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
Return source
Return condition
Remarks
Ports P0, P1 Return by an external falling edge Port P0 shares the falling edge detection circuit with ports P1 and P4.
and P4
input (“H”→“L”).
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.
P21/INT pin Return by an external “H” level or Select the return level (“L” level or “H” level) with the bit 2 of register I1
“L” level input.
according to the external state before going into the RAM back-up mode.
The EXF0 flag is not set.
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