R8C/36T-A Group
29. Usage Notes
Under development Preliminary document
Specifications in this document are tentative and subject to change.
R01UH0241EJ0010 Rev.0.10
Page 719 of 728
Aug 05, 2011
29.16.1.3 How to Access
To set one of the following bits to 1, first write 0 and then 1 immediately. Disable interrupts and DTC activation
between writing 0 and writing 1.
The FMR01 bit or FMR02 bit in the FMR0 register
The FMR13 bit in the FMR1 register
The FMR20 bit, FMR22 bit, or FMR 27 bit in the FMR2 register
To set one of the following bits to 0, first write 1 and then 0 immediately. Disable interrupts and DTC activation
between writing 1 and writing 0.
The FMR14 bit, FMR15 bit, FMR16 bit, or FMR17 bit in the FMR1 register
29.16.1.4 Rewriting User ROM Area
In EW0 mode, if the supply voltage drops while rewriting any block in which a rewrite control program is
stored, it may not be possible to rewrite the flash memory because the rewrite control program cannot be
rewritten correctly. In this case, use standard serial I/O mode.
29.16.1.5 Programming
Do not write additions to the already programmed address.
29.16.1.6 Entering Stop Mode or Wait Mode
Do not enter stop mode or wait mode during erase-suspend.
If the FST7 bit in the FST register is set to 0 (busy during programming or erasure execution), do not enter to
stop mode or wait mode.
Do not enter stop mode or wait mode while the FMR27 bit is 1 (low-current-consumption read mode enabled).
29.16.1.7 Programming and Erasure Voltage for Flash Memory
To perform programming and erasure, use VCC = 2.7 to 5.5 V as the supply voltage. Do not perform
programming and erasure at less than 2.7 V.
29.16.1.8 Block Blank Check
Do not execute the block blank check command during erase-suspend.
29.16.1.9 Low-Current-Consumption Read Mode
In low-speed clock mode and low-speed on-chip oscillator mode, the current consumption when reading the
flash memory can be reduced by setting the FMR27 bit in the FMR2 register to 1 (low-current-consumption
read mode enabled).
Low-current-consumption read mode can be used when the CPU clock is set to either of the following:
The CPU clock is set to the low-speed on-chip oscillator clock divided by 4, 8, or 16.
The CPU clock is set to the XCIN clock divided by 1 (no division), 2, 4, or 8.
However, do not use low-current-consumption read mode when the frequency of the selected CPU clock is
3 kHz or below. After setting the divide ratio of the CPU clock, set the FMR27 bit to 1 (low-current-
consumption read mode enabled).
To reduce the power consumption, refer to 10. Power Control.
Enter wait mode or stop mode after setting the FMR27 bit to 0 (low-current-consumption read mode disabled).
Do not enter wait mode or stop mode while the FMR27 bit is 1 (low-current-consumption read mode enabled).