M16C30P_07 Datasheet, PDF (287/317 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/30 SERIES

M16C/30P Group
22. Usage Precaution
• Suggestions to reduce power consumption
Ports
The processor retains the state of each I/O port even when it goes to wait mode or to stop mode. A current
flows in active I/O ports. A pass current flows in input ports that high-impedance state. When entering wait
mode or stop mode, set non-used ports to input and stabilize the potential.
A/D converter
When A/D conversion is not performed, set the VCUT bit of ADiCON1 register to “0” (no VREF
connection).
When A/D conversion is performed, start the A/D conversion at least 1 μs or longer after setting the VCUT bit
to “1” (VREF connection).
Stopping peripheral functions
Use the CM0 register CM02 bit to stop the unnecessary peripheral functions during wait mode.
However, because the peripheral function clock (fC32) generated from the sub-clock does not stop, this
measure is not conducive to reducing the power consumption of the chip. If low speed mode or low power
dissipation mode is to be changed to wait mode, set the CM02 bit to “0” (do not peripheral function clock
stopped when in wait mode), before changing wait mode.
Switching the oscillation-driving capacity
Set the driving capacity to “LOW” when oscillation is stable.
22.5 Precautions for Protect
Set the PRC2 bit to “1” (write enabled) and then write to any address, and the PRC2 bit will be cleared to “0” (write
protected). The registers protected by the PRC2 bit should be changed in the next instruction after setting the PRC2
bit to “1”. Make sure no interrupts or DMA transfers will occur between the instruction in which the PRC2 bit is set
to “1” and the next instruction.
Rev.1.22 Mar 29, 2007 Page 271 of 291
REJ09B0179-0122