EM78F651NAM datasheet(35/58 Pages) EMC

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EM78F651N

8-Bit Microcontroller

Product Specification (V1.1) 10.20.2006

• 31

(This specification is subject to change without further notice)

Vdd, is below the working voltage, the IC kernel must keep all register status

automatically.

LVD property is set at Register RE, Bit 1, 0 detailed operation mode is as follows:

Bits 1~Bit 0 (LVD1~LVD0): Low Voltage Detect level control Bits.

LVD1

LVD0

LVD Voltage Interrupt Level

2.1

3.1

3.8

4.3

The LVD status and interrupt flag is referred to as RF

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

LVDIF

EXIF

ICIF

TCIF

Bit 7 (LVDIF): Low voltage Detector interrupt flag.

When LVD1, LVD0 = “0, 0”, Vdd > 2.3V, LVDIF is “0”, Vdd

≤ 2.3V, set LVDIF to “1”.

LVDIF is reset to “0” by software.

When LVD1, LVD0 = “0, 1”, Vdd > 3.3V, LVDIF is “0”, Vdd

≤ 3.3V, set LVDIF to “1”.

LVDIF is reset to “0” by software.

When LVD1, LVD0 = “1, 0”, Vdd > 4.0V, LVDIF is “0”, Vdd

≤ 4.0V, set LVDIF to “1”.

LVDIF is reset to “0” by software.

When LVD1, LVD0 = “1, 1”, Vdd > 4.5V, LVDIF is “0”, Vdd

≤ 4.5V, set LVDIF to “1”.

LVDIF is reset to “0” by software.

The following steps are needed to setup the LVD function:

Set the LVDEN of Register RE to “1”, then use Bit 1, 0 (LVD1, LVD0) of Register RE

to set LVD interrupt level

Wait for LVD interrupt to occur.

Clear LVD interrupt flag

The internal LVD module uses internal circuit to fit. When the LVDEN is set to enable

the LVD module, the current consumption will increase to about 10µA.

During sleep mode, the LVD module continues to operate. If the device voltage

drops slowly and crosses the detect point, the LVDIF bit will be set and the device

won’t wake-up from Sleep mode. Until the other wake-up sources wake up the

device, the LVD interrupt flag is still set at the prior status.

When the system resets, the LVD flag will be cleared.

Figure 6-9 shows the LVD module to detect the external voltage situation.

When Vdd drops not below VLVD, LVDIF remain at “0”.

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