EM78P568

8-bit OTP Micro-controller

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* This specification are subject to be changed without notice.

49

01/31/2004

V4.7

VII.12 4-bit Comparator

PORT62

MUX

CMP1

P62S

PORT63

MUX

CMP2

P63S

PORT64

MUX

CMP3

P64S

MUX

CMPS1

CMPS0

+

-

MUX

CMPREF

CMPFLAG

CMPEN

0

1

2

CMP1/P62

CMP2/P63

CMP3/P64

MUX

1/2R

R

R

1/2R

5

CMP_B4 to CMP_B0

11111

11110

00000

VRSEL

MUX

2.5V

ref

2.5V

REFEN

(This ckt is form DAC)

VR

VDD

Name

Register bit location

CMPEN

IOC5 PAGE1 bit 7

CMPS1 ~ CMPS0

IOC5 PAGE1 bit 6 ~ 5

CMP_B4 ~ CMP_B0

IOC5 PAGE1 bit 4 ~ 0

Name

Register bit location

CMPREF

RA PAGE0 bit 1

CMPFLAG

RA PAGE0 bit 2

Name

Register bit location

P62S

IOC6 PAGE1 bit 2

P63S

IOC6 PAGE1 bit 3

P64S

IOC6 PAGE1 bit 4

VRSEL

IOCA PAGE1 bit 4

This comparator is not only a single comparator. It consists of 16-R resistor string, 3-channel input and optional

external comparison reference source input. The 16-R resistor string acts as 16-level voltage divider which top

voltage reference can be selected from VDD or 2.5V ref. Use above register bits to set the whole job. This

comparator is used to some applications such as voltage detection, RSSI level, sensor output level and other slow

signal level transition detection and so on. This comparator can be called a simple 4-bit low speed ADC but the

sampling time is decided by software. For AC frequency detection, it is limited by it output comparator structure.

We suggest the detected AC frequency below 1kHz.