r5f21346mnfp Renesas Electronics Corporation., r5f21346mnfp Datasheet - Page 701

• Manufacturer Part Number: r5f21346mnfp
• Description: Single-chip Mcus Incorporates The R8c Cpu Core
• Manufacturer: Renesas Electronics Corporation.

R8C/34M Group
R01UH0131EJ0100 Rev.1.00
Jun 21, 2011
33. Reducing Power Consumption
33.1
33.2
33.2.1
33.2.2
33.2.3
33.2.4
33.2.5
33.2.6
33.2.7
33.2.8
This chapter describes key points and processing methods for reducing power consumption.
Key points for reducing power consumption are shown below. They should be referred to when designing a system
or creating a program.
If voltage monitor 1 and comparator A1 are not used, set the VCA26 bit in the VCA2 register to 0 (voltage
detection 1 circuit disabled). If voltage monitor 2 and comparator A2 are not used, set the VCA27 bit in the
VCA2 register to 0 (voltage detection 2 circuit disabled).
If the power-on reset and voltage monitor 0 reset are not used, set the VCA25 bit in the VCA2 register to 0
(voltage detection 0 circuit disabled).
Even after the MCU enters wait mode or stop mode, the states of the I/O ports are retained. Current flows into
the output ports in the active state, and shoot-through current flows into the input ports in the high-impedance
state. Unnecessary ports should be set to input and fixed to a stable electric potential before the MCU enters
wait mode or stop mode.
Power consumption generally depends on the number of the operating clocks and their frequencies. The fewer
the number of operating clocks or the lower their frequencies, the more power consumption decreases.
Unnecessary clocks should be stopped accordingly.
Stopping low-speed on-chip oscillator oscillation: Set the CM14 bit in the CM1 register to 1 (low-speed on-
Stopping high-speed on-chip oscillator oscillation: Set the FRA00 bit in the FRA0 register to 0.
Power consumption can be reduced in wait mode and stop mode. Refer to 9.7 Power Control for details.
If the peripheral function f1, f2, f4, f8, and f32 clocks are not necessary in wait mode, set the CM02 bit in the
CM0 register to 1 (peripheral function clock stops in wait mode). This will stop the f1, f2, f4, f8, and f32 clocks
in wait mode.
If timer RA is not used, set the TCKCUT bit in the TRAMR register to 1 (count source cutoff).
If timer RB is not used, set the TCKCUT bit in the TRBMR register to 1 (count source cutoff).
If timer RC is not used, set the MSTTRC bit in the MSTCR register to 1 (standby).
If timer RD is not used, set bits TCK2 to TCK0 in the TRDCRi (i = 0 to 1) register to 000b (f1) and the
MSTTRD bit in the MSTCR register to 1 (standby).
When the A/D converter is not used, power consumption can be reduced by setting the ADSTBY bit in the
ADCON1 register to 0 (A/D operation stops (standby)) to shut off any analog circuit current flow.
When the SSU or the I
Overview
Key Points and Processing Methods for Reducing Power Consumption
Voltage Detection Circuit
Ports
Clocks
Wait Mode, Stop Mode
Stopping Peripheral Function Clocks
Timers
A/D Converter
Clock Synchronous Serial Interface
2
C bus is not used, set the MSTIIC bit in the MSTCR register to 1 (standby).
chip oscillator off) and the OCD2 bit in the OCD register to
0 (XIN clock selected).
33. Reducing Power Consumption
Page 669 of 740