HT85F2270 datasheet(154/226 Pages) HOLTEK

154 / 226 page

Rev. 1.00

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Standard 8051 8-Bit Flash MCU

HT85F2260/HT85F2270/HT85F2280

A/D Converter Register Description

A read only register pair exists to store the ADC data 12-bit value. The remaining registers are

control registers which setup the operating and control function of the A/D converter.

A/D Converter Register List

Name

Bit

ADRL(ADRFS=0)

D�

—

ADRL(ADRFS=1)

D�

ADRH(ADRFS=0)

D11

D10

D�

ADRH(ADRFS=1)

—

D11

D10

ADCR0

START

EOCB

ADOFF

ADRFS

ACS�

ACS1

ACS0

ADCR1

ACS4

TSEN

—

VREFAS VREFIS

ADCK�

ADCK1

ADCK0

ADCR�

ACE7

ACE6

ACE�

ACE4

ACE�

ACE1

ACE0

ADPGA

—

ADGN�

ADGN1

ADGN0

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. As only 12 bits of the 16-bit register space

is utilised, the format in which the data is stored is controlled by the ADRFS bit in the ADCR0

unused bits will be read as zero.

A/D Data Registers

ADRFS

ADRH

ADRL

D11 D10

D�

D11 D10

D�

A/D Converter Control Registers – ADCR0, ADCR1, ADCR2, ADPGA

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

ADCR0, ADCR1, ADCR2 and ADPGA are provided. These 8-bit registers define functions such

as analog channel selection, converted data format, PGA gain, clock source as well as the start

bit and end of conversion flag. As the device contains only one actual analog to digital converter

hardware circuit, each of the individual 8 analog inputs must be routed to the converter. It is the

function of the ACS4~ACS0 bits to determine which analog channel input pin, reference voltage or

internal temperature sensor is actually connected to the internal A/D converter.

The ADCR2 control register bits determine whether the pins on Port 4 are to be used as A/D

converter analog inputs or used as logic I/O pins. Setting the corresponding bit high will select the

A/D input function, clearing the bit to zero will select the I/O function. When the pin is selected

to be an A/D input, its logic I/O function will be removed and any internal pull-high resistors

connected to these pins will be automatically removed.

The ADPGA register determines the gain of the Programmable Gain Amplifier which is used to

amplify the analog input signal before conversion by the A/D Converter.

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