Ram Backup State - Mitsubishi 32172 User Manual

19

19.2.2 RAM Backup State

Shown in Figure 19.2.3 is the power outage RAM backup state of the M32R/E. When the power
supply goes down, the power supply monitor IC starts feeding current from the backup battery to
the M32R/E. Also, the power supply monitor IC's power outage detection pin outputs a low, causing
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the SBI pin or ADnINi pin input to go low, which generates a RAM backup signal (
17.2.3). Whether the power is down or not must be determined with respect to the DC IN (regulator
input) voltage in order to allow for a software processing time at power outage.
To enable RAM backup mode, make the following settings.
(1) Create check data to verify after returning from RAM backup to normal mode whether the
RAM data has been retained normally (
When the power supply to VCC goes down after settings in (1), the voltage applied to the VDD pin
becomes 2.0-3.3 V and voltages applied to all other pins drop to 0 V, and the M32R/E thereby
enters RAM backup mode (
DC IN
Input
Regulator
(5V system)
Regulator
(3.3V system)
(Note 1)
Reference voltage for
power outage detection
(Note 4)
Backup battery
Example of RAM backup processing
Power goes down (Note 4)
Create check data
for backup RAM
RAM backup mode
Figure 19.2.3 RAM Backup State at Power Outage
19.2 Example of RAM Backup when Power is Down
in Figure 19.2.3).
Output
Output
Power supply
C
monitor IC
(Note 5)
VCC VDD
VREF
OUT
VBB
in Figure 19.2.3).
Backup power supply
for power outage
2.0V - 3.3V
0V
3.3V
VDD VCCI
(Note 3)
Power outage
SBI
detection signal
(Note 2)
ADnINi
"L"
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.
Note 4: Determined by the input voltage level on SBI
pin or ADnINi pin.
Note 5: Adjust this capacitance to provid the
necessary processing time in
19-4
RAM BACKUP MODE
in Figure
0V 0V 0V
OSC-VCC VCCE VREFn AVCCn
M32R/E
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.
Rev.1.0
0V