Normal Operating State - Renesas M32R/ECU Series User Manual

17
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.
DC IN Input
Regulator
Reference voltage for
power outage detection
Backup battery
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.
Figure 17.2.1 Typical Circuit for RAM Backup at Power Outage

17.2.1 Normal Operating State

Figure 17.2.2 shows the normal operating state of the M32R/ECU. During normal operation, input on the SBI#
pin or ADnINi (i = 0–15) pin which is used to detect a RAM backup signal remains high.
DC IN
Input
Regulator
Reference voltage for
power outage detection
Backup battery
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: Backup power supply = 3.0 to 5.5 V
Figure 17.2.2 Normal Operating State (when VCCE = 5 V)
17.2 Example of RAM Backup when Power is Down
Output
C
Power supply monitor IC
Backup power supply
for power outage
VCC VDDE
(Note 1)
VREF
Power outage
detection signal
OUT
VBB
Output
C
Power supply monitor IC
Backup power supply
for power outage
VCC VDDE
(Note 1)
VREF
Power outage
detection signal
OUT
VBB
"H"
VDDE VCCE VREFn
(Note 3)
SBI#
(Note 2)
ADnINi
(Note 4)
5V
VDDE VCCE VREFn
(Note 3)
SBI#
(Note 2)
ADnINi
17-3
RAM BACKUP MODE
AVCCn VCC-BUS OSC-VCC
M32R/ECU
5V 5V 5V 5V
AVCCn VCC-BUS OSC-VCC
M32R/ECU
32180 Group User's Manual (Rev.1.0)