
RAM BACKUP MODE
19
19-4
32185/32186 Group Hardware Manual
Rev.1.10 REJ09B0235-0110 May 15, 07
(a)
(b)
(c)
"L"
0V
VREF0
SBI#
AD0INi
M32R/ECU
C
VCC
VDD
VBB
VREF
DC IN
(5V or 3.3V)
VDDE
AVCC0
OUT
VCCE,
VCCER
EXCVCC
EXCVDD
VCC-
BUS
(Note 2)
Backup battery
Reference voltage for
power outage detection
Power outage
detection signal
Backup power supply
for power outage
Power supply monitor IC
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 "H" when the power is on and outputs "L" when the power is off.
Note 4: Determined by the input level on SBI# pin or AD0INi pin.
Note 5: The time needed for processing in (b) is secured by adjusting the capacitance.
Input
Output
Regulator
(Note 3)
(Note 1)
(Note 5)
3.3V or 5.0V
Example of RAM backup processing
Power goes off
(Note 4)
Create data for
backup RAM check
RAM backup mode
19.2 Example of RAM Backup when Power is Off
19.2.2 RAM Backup State
Figure 19.2.3 shows the power outage RAM backup state of the M32R/ECU. When the power supply goes
off, the power supply monitor IC starts feeding current from the backup battery to the M32R/ECU. Also, the
power supply monitor IC’s power outage detection pin outputs "L," causing the SBI# pin or AD0INi pin to go
"L," which generates a RAM backup signal ((a) in Figure 19.2.3). Determination of whether the power is off
must be made 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 setting:
(1) Create data for RAM check to verify whether the RAM data has been retained normally after
returning from RAM backup mode to normal mode ((b) in Figure 19.2.3).
If the power supply to VCCE goes off after making above setting, the VDDE pin voltage goes to 3.0–3.3 V and all
other pin voltages drop to 0 V, and the M32R/ECU is thereby placed in RAM backup mode ((c) in Figure 19.2.3).
Figure 19.2.3 Power Outage RAM Backup State