HT48R02B datasheet(43/71 Pages) HOLTEK

43 / 71 page

HT46R01B/02B/01N/02N

HT48R01B/02B/01N/02N

Rev.1.00

December 15, 2009

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 device contains an 4-channel analog to digital con-

verter which can directly interface to external analog sig-

nals, such as that from sensors or other control signals

and convert these signals directly into either a 12-bit dig-

ital value.

The accompanying block diagram shows the overall in-

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

sociated registers.

A/D Converter Data Registers

- ADRL, ADRH

The device, which has an internal 12-bit A/D converter,

requires two data registers, 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 digit-

ised conversion value. Only the high byte register,

ADRH, utilises its full 8-bit contents. The low byte regis-

ter utilises only 4 bit of its 8-bit contents as it contains

only the lowest bits of the 12-bit converted value.

In the following table, D0~D11 is the A/D conversion

data result bits.

Bit

ADRL

¾¾¾¾

ADRH

D11 D10 D9

A/D Data Registers

A/D Converter Control Registers

- ADCR, ACSR

To control the function and operation of the A/D con-

verter, two control registers known as ADCR and ACSR

are provided. These 8-bit registers define functions

such as the selection of which analog channel is con-

nected to the internal A/D converter, which pins are

used as analog inputs and which are used as normal

I/Os, the A/D clock source as well as controlling the start

function and monitoring the A/D converter end of con-

version status.

The ACS1~ACS0 bits in the ADCR register define the

channel number. As the device contains only one actual

analog to digital converter circuit, each of the individual

4 analog inputs must be routed to the converter. It is the

function of the ACS1~ACS0 bits in the ADCR register to

determine which analog channel is actually connected

to the internal A/D converter.

C l o c k

D i v i d e r

A C S R R e g i s t e r

A D C

A D R L

A D R H

A / D D a t a

R e g i s t e r s

P C R 0 ~ P C R 3

A D C S 0 ~ A D C S 2

S T A R T

E O C B

A D C R

R e g i s t e r

A D O N B B i t

A / D E n a b l e

f S Y S

P A 0 / A N 0

P A 1 / A N 1

P A 2 / A N 2

P A 3 / A N 3

A/D Converter Structure

HT48R02B Datasheet(PDF) 43 Page - Holtek Semiconductor Inc

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