HT45F23 datasheet(75/152 Pages) HOLTEK

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A/D Converter Data Registers

- ADRL, ADRH

As the devices contain an internal 12-bit A/D converter, they require two data registers to store the

converted value. These are a high byte register, known as ADRH, and a low byte register, known as

ADRL. After the conversion process takes place, these registers can be directly read by the

microcontroller to obtain the digitised conversion value. D0~D11 are the A/D conversion result data

bits. Any unused bits will be read as zero.

ADRH

ADRL

7654321076543210

D11

D10

0000

A/D Data Registers

A/D Converter Control Registers

- ADCR, ACSR, ADPCR

To control the function and operation of the A/D converter, three control registers known as ADCR,

ACSR and ADPCR are provided. These 8-bit registers define functions such as the selection of which

analog channel is connected to the internal A/D converter, the digitised data format, the A/D clock

source as well as controlling the start function and monitoring the A/D converter end of conversion

status. The ACS2~ACS0 bits in the ADCR register define the ADC input channel number. As the

device contains only one actual analog to digital converter hardware circuit, each of the individual 8

analog inputs, which include 6 external A/D channels and 2 internal OPA outputs, must be routed to

the converter. It is the function of the ACS2~ACS0 bits to determine which analog channel input pin is

actually connected to the internal A/D converter.

The ADPCR control register contains the PCR5~PCR0 bits which determine which pins on Port B and

Port C are used as analog inputs for the A/D converter input and which pins are not to be used as the

A/D converter input. Setting the corresponding bit high will select the A/D input function, clearing the

bit to zero will select either the I/O or other pin-shared function. When the pin is selected to be an A/D

input, its original function whether it is an I/O or other pin-shared function will be removed. In

addition, any internal pull-high resistors connected to these pins will be automatically removed if the

pin is selected to be an A/D input.

ADCR Register

Bit

76543210

Name

START

EOCB

¾¾¾

ACS2

ACS1

ACS0

R/W

¾¾¾

R/W

POR

¾¾¾

000

Bit 7

START: Start the A/D conversion

®1®0 : start

®1

: reset the A/D converter and set EOCB to

²1²

This bit is used to initiate an A/D conversion process. The bit is normally low but if set high and

then cleared low again, the A/D converter will initiate a conversion process. When the bit is set

high the A/D converter will be reset.

Bit 6

EOCB: End of A/D conversion flag

0: A/D conversion ended

1: A/D conversion in progress

This read only flag is used to indicate when an A/D conversion process has completed. When

the conversion process is running the bit will be high.

Bit 5~3

unimplemented, read as

²0²

HT45F23/HT45F43

8-Bit Flash MCU with Op Amps & Comparators

Rev. 1.20

September 15, 2011

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