R8CSLASH2G datasheet(294/344 Pages) RENESAS

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R8C/2G Group

21. Reducing Power Consumption

Rev.1.00

Apr 04, 2008

Page 274 of 318

REJ09B0387-0100

21.2.10 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 FMR47 bit in the FMR4 register to 1 (enabled).

Figure 21.3 shows the Handling Procedure Example of Low-Current-Consumption Read Mode.

Figure 21.3

Handling Procedure Example of Low-Current-Consumption Read Mode

NOTES:

1. To set the FMR47 bit to 1, first write 0 and then write 1 immediately.

After writing 0, do not generate an interrupt before writing 1.

2. In low-current-consumption read mode, set the FMR01 bit in the FMR0 register to 0 (CPU rewrite mode disabled).

Handling procedure of

low-current-consumption read mode

enabled by FMR47 bit

Enter low-speed clock mode or

low-speed on-chip oscillator mode

Stop high-speed on-chip oscillator clock

FMR47

← 1 (low-current-consumption read

mode enabled)(1)

Enter low-current-consumption read mode(2)

FMR47

← 0 (low-current-consumption read

mode disabled)

Start high-speed on-chip oscillator clock

(Wait until high-speed on-chip oscillator clock

oscillation stabilizes)

Enter high-speed on-chip oscillator mode

Step (1)

Step (2)

Step (3)

Step (4)

Step (5)

Step (6)

Step (7)

Step (8)

FMR47: Bit in FMR4 register

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