4513 datasheet(47/97 Pages) RENESAS

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4513/4514 Group

SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

Voltage comparator control register Q3 (Note 2)

at reset : 00002

at RAM back-up : state retained

Q33

Q32

Q31

Q30

Voltage comparator (CMP1) invalid

Voltage comparator (CMP1) valid

Voltage comparator (CMP0) invalid

Voltage comparator (CMP0) valid

CMP1- > CMP1+

CMP1- < CMP1+

CMP0- > CMP0+

CMP0- < CMP0+

Voltage comparator (CMP1) control bit

Voltage comparator (CMP0) control bit

CMP1 comparison result store bit

CMP0 comparison result store bit

Notes 1: “R” represents read enabled, and “W” represents write enabled.

2: Bits 0 and 1 of register Q3 can be only read.

(1) Voltage comparator control register Q3

The function of the voltage comparator CMP0 becomes valid by

setting bit 2 of register Q3 to “1,” and becomes invalid by setting bit

2 of register Q3 to ”0.” The comparison result of the voltage com-

parator CMP0 is stored into bit 0 of register Q3.

The function of the voltage comparator CMP1 becomes valid by

setting bit 3 of register Q3 to “1,” and becomes invalid by setting bit

3 of register Q3 to ”0.” The comparison result of the voltage com-

parator CMP1 is stored into bit 1 of register Q3.

(2) Operation description of voltage

comparator

The voltage comparator function becomes valid by setting each

control bit of register Q3 to “1” and compares the voltage of the in-

put pin. The comparison result is stored into each comparison

result store bit of register Q3.

The comparison result is as follows;

• When CMP0- > CMP0+, Q30 = “0”

When CMP0- < CMP0+, Q30 = “1”

• When CMP1- > CMP1+, Q31 = “0”

When CMP1- < CMP1+, Q31 = “1”

(3) Precautions

When the voltage comparator is used, note the following;

• Voltage comparator function

When the voltage comparator function is valid with the voltage

comparator control register Q3, it is operating even in the RAM

back-up mode. Accordingly, be careful about such state because

it causes the increase of the operation current in the RAM back-

up mode.

In order to reduce the operation current in the RAM back-up

mode, invalidate (bits 2 and 3 of register Q3 = “0”) the voltage

comparator function by software before the POF instruction is

executed.

Also, while the voltage comparator function is valid, current is al-

ways consumed by voltage comparator. On the system required

for the low-power dissipation, invalidate the voltage comparator

by software when it is unused.

• Register Q3

Bits 0 and 1 of register Q3 can be only read. Note that they can-

not be written.

• Reading the comparison result of voltage comparator

Read the voltage comparator comparison result from register Q3

after the voltage comparator response time (max. 20

µs) is

passed from the voltage comparator function becomes valid.

R/W

Table 18 Voltage comparator control register Q3

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