Precautions To Be Observed At Power-On - Mitsubishi Electric M32R Series User Manual

17
Power on
VCCE,
VREFn, AVCCn
VCCI,
OSC-VCC
VDD
Port X
SBI
ADnINi
f (XIN)
RESET
Figure 17.3.4 Example of 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 indeterminate. Therefore, be sure to set the output high level in the Port X Data
Register before you set port X for output mode. Unless this method is followed, port output may go
low at the same time port output is set after the clock oscillation has stabilized, causing the device
to enter RAM backup mode.
17.3 Example of RAM Backup for Saving Power Consumption
5.0V
3.3V
Port output setting
(High level)
External input
signal goes low
Oscillation
stabilization time
17-8
RAM BACKUP MODE
RAM backup
period
0V
0V
Port input
mode
External input
signal goes high
Oscillation
stabilization time
Port output setting
(High level)
Ver.0.10