Precautions To Be Observed At Power-On - Renesas M32R/ECU Series User Manual

17
Power on
VCCE,
VREFn , AVCCn
VCC-BUS,OSC-VCC
VDDE
Port X
SBI#
ADnINi
f(XIN)
RESET#
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.
17.3 Example of RAM Backup for Saving Power Consumption
5.0V or 3.3V
Port output setting
(high level)
External input signal
goes low
Oscillation
stabilization time
17-7
RAM BACKUP MODE
RAM backup
period
0V
Port input Port output setting
mode
External input signal
goes high
Oscillation
stabilization time
32180 Group User's Manual (Rev.1.0)
(high level)