R8C2K datasheet(418/471 Pages) RENESAS

418 / 471 page

R8C/2K Group, R8C/2L Group

21. Reducing Power Consumption

Rev.1.10

Dec 21, 2007

Page 401 of 450

REJ09B0406-0110

21.2.10 Low-Current-Consumption Read Mode

In 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

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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