HT68F03 datasheet(95/139 Pages) HOLTEK

95 / 139 page

HT66F03/HT66F04/HT68F03/HT68F04

Rev. 1.00

April 16, 2010

Analog to Digital Converter

The need to interface to real world analog signals is a

common requirement for many electronic systems.

However, to properly process these signals by a

microcontroller, they must first be converted into digital

signals by A/D converters. By integrating the A/D con-

version electronic circuitry into the microcontroller, the

need for external components is reduced significantly

with the corresponding follow-on benefits of lower costs

and reduced component space requirements.

A/D Overview

The devices contains a multi-channel analog to digital

converter which can directly interface to external analog

signals, such as that from sensors or other control sig-

nals and convert these signals directly into either a

12-bit digital value.

Part No.

Input

Channels

A/D Channel

Select Bits

Input

Pins

HT66F03

HT66F04

ACS4,

ACS1~ACS0

AN0~AN3

The accompanying block diagram shows the overall in-

ternal structure of the A/D converter, together with its as-

sociated registers.

A/D Converter Register Description

Overall operation of the A/D converter is controlled us-

ing six registers. A read only register pair exists to store

the ADC data 12-bit value. The remaining three or four

registers are control registers which setup the operating

and control function of the A/D converter.

Name

Bit

76543210

ADRL(ADRFS=0)

¾¾¾¾

ADRL(ADRFS=1)

ADRH(ADRFS=0)

D11

D10

ADRH(ADRFS=1)

¾¾¾¾

D11

D10

ADCR0

START

EOCB

ADOFF

ADRFS

¾¾

ACS1

ACS0

ADCR1

ACS4

V125EN

VREFS

ADCK2

ADCK1

ADCK0

ACERL

¾¾¾¾

ACE3

ACE2

ACE1

ACE0

HT66F03/HT66F04 A/D Converter Register List

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 register as shown in the accompanying table. D0~D11 are the A/D conversion result data bits. Any unused bits

will be read as zero.

ADRFS

ADRH

ADRL

7654321076543210

D11

D10

0000

D11

D10

A/D Data Registers

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