17
17-2
Ver.0.10
17.1 Outline
In RAM backup mode, the contents of the internal RAM are retained while the power is turned off.
RAM backup mode is used for the following two purposes:
• Back up the internal RAM data when the power is down
• Turn off the power to the CPU whenever necessary to save on the system's power
consumption
The 32R/E CPU is placed in RAM backup mode by applying a voltage of 2.0-3.3 V to the VDD pin
(provided for RAM backup) and 0 V to all other pins. During RAM backup mode, the contents of the
internal RAM are retained, while the CPU and internal peripheral I/O remain idle. Also, because all
pins except VDD are held low during RAM backup mode, power consumption in the system can
effectively reduced.
17.2 Example of RAM Backup when Power is Down
A typical circuit for RAM backup at power outage is shown in Figure 17.2.1. The following explains
how the RAM can be backed up by using this circuit as an example.
RAM BACKUP MODE
17.1 Outline
Figure 17.2.1 Typical Circuit for RAM Backup at Power Outage
Note 1 : Power outage is detected by the DC IN (regulator input) voltage.
Note 2 : These pins are used to detect a RAM backup signal.
Note 3 : This pin outputs a high when the power is on and outputs a low when the power is down.
VREFn
SBI
ADnINi
M32R/E
C
Backup battery
VCC
VDD
VBB
VREF
Reference voltage for
power outage detection
Power outage
detection signal
Backup power supply
for power outage
Power supply
monitor IC
VDD
DC IN
Input
Output
Regulator
(5V system)
VCCI
AVCCn
OSC-VCC
OUT
VCCE
(Note 1)
Output
Regulator
(3.3V system)
(Note 3)
(Note 2)
Summary of Contents for M32170F3VFP
Page 42: ...1 1 24 Ver 0 10 OVERVIEW 1 4 Pin Layout This is a blank page ...
Page 56: ...2 2 14 Ver 0 10 This is a blank page ...
Page 88: ...3 3 32 Ver 0 10 ADDRESS SPACE 3 7 Notes on Address Space This is a blank page ...
Page 270: ...9 9 40 Ver 0 10 DMAC 9 4 Precautions about the DMAC This is a blank page ...
Page 614: ...12 12 64 Ver 0 10 This is a blank page SERIAL I O 12 9 Precautions on Using UART Mode ...
Page 756: ...17 17 10 Ver 0 10 RAM BACKUP MODE 17 4 Exiting RAM Backup Mode Wakeup This is a blank page ...
Page 762: ...18 18 6 Ver 0 10 OSCILLATION CIRCUIT 18 2 Clock Generator Circuit This is a blank page ...
Page 831: ...CHAPTER 22 CHAPTER 22 TYPICAL CHARACTERISTICS 22 1 A D Conversion Characteristics ...
Page 833: ...Appendix 1 1 Dimensional Outline Drawing APPENDIX 1 APPENDIX 1 MECHANICAL SPECIFICATIONS ...
Page 841: ...Appendix 3 1 Precautions about Noise APPENDIX 3 APPENDIX 3 PRECAUTIONS ABOUT NOISE ...