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17-3

RAM BACKUP MODE

32180 Group User's Manual (Rev.1.0)

Figure 17.2.1 Typical Circuit for RAM Backup at Power Outage

VREFn

SBI#

ADnINi

M32R/ECU

(Note 2)

Backup battery

VCC VDDE

VBB

VREF

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 a high when the power is on and outputs a low when the power is down.

VDDE

DC IN

Input Output

Regulator

AVCCn VCC-BUS OSC-VCC

OUT

(Note 3)

VCCE

(Note 1)

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.

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.

Figure 17.2.2 Normal Operating State (when VCCE = 5 V)