17
17-7
RAM BACKUP MODE
32180 Group User's Manual (Rev.1.0)
17.3 Example of RAM Backup for Saving Power Consumption
RESET#
SBI#
ADnINi
VDDE
Oscillation
stabilization time
External input signal
goes low
RAM backup
period
Power on
Port output setting
(high level)
External input signal
goes high
Port X
Port input
mode
f(XIN)
VCCE,
VREFn , AVCCn
5.0V or 3.3V
0V
VCC-BUS,OSC-VCC
Port output setting
(high level)
Oscillation
stabilization time
Figure 17.3.4 Example of a RAM Backup Sequence for Low Power Operation
17.3.3 Precautions to Be Observed at Power-On
When changing port X from input mode to output mode after power-on, pay attention to the following.
If port X is set for output mode while no data is set in the Port X Data Register, the port’s initial output level is
instable. Therefore, before changing port X for output mode, make sure the Port X Data Register is set to output
a high.
Unless this precaution is followed, port output may go low at the same time the port is set for output after the
oscillation has stabilized, causing the microcomputer to enter RAM backup mode.
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