Renesas M32R/ECU Series User Manual page 824

SUMMARY OF PRECAUTIONS
Appendix 4
Appendix 4.11 Precautions about RAM Backup Mode
Appendix 4.11 Precautions about RAM Backup Mode
Appendix 4.11.1 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.
Appendix 4-19
32180 Group User's Manual (Rev. 1.0)