HT48R005 datasheet(37/62 Pages) HOLTEK

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HT48R005/HT46R005

Rev. 1.00

November 29, 2011

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 HT46R005 contains a 3-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.

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 four registers. A read only register pair exists to store

the ADC data 12-bit value. The remaining two registers

are control registers which setup the operating and con-

trol function of the A/D converter.

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 con-

version process takes place, these registers can be di-

rectly read by the microcontroller to obtain the digitised

conversion value. Only the high byte register, ADRH,

utilises its full 8-bit contents. The low byte register uti-

lises 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.

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 2

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

P i n C o n f i g u r a t i o n

B i t s

C h a n n e l S e l e c t

B i t s

S t a r t B i t E n d o f

C o n v e r s i o n B i t

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

V D D

A D O N B i t

A C S R

R e g i s t e r

A/D Converter Structure

In the following table, D0~D11 is the A/D conversion data result bits.

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

ADRL

¾¾¾¾

ADRH

D11

D10

ADCR

START

EOCB

PCR2

PCR1

PCR0

ACS1

ACS0

ACSR

TEST

ADONB

¾¾¾

ADCS2

ADCS1

ADCS0

A/D Data Registers

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