HT66F20 datasheet(132/250 Pages) HOLTEK

132 / 250 page

HT66F20/HT66F30/HT66F40/HT66F50/HT66F60

HT66FU30/HT66FU40/HT66FU50/HT66FU60

Rev. 1.20

132

June 4, 2010

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

A / D C o n v e r t e r

P A 0 / A N 0 ~ P A 7 / A N 7

P E 6 / A N 8

P E 7 / A N 9

P F 0 / A N 1 0

P F 1 / A N 1 1

A / D R e f e r e n c e V o l t a g e

A D R L

A D R H

A / D D a t a

R e g i s t e r s

V 1 2 5 E N

S T A R T

E O C B

A D O F F

V S S

P B 5 / V R E F

A D C K 2 ~ A D C K 0

f S Y S

A C E 1 1 ~ A C E 0

A C S 4 ~ A C S 0

1 . 2 5 V

A / D C l o c k

V D D

A D O F F

B i t

V R E F S

B i t

A D R F S

b i t

¸ 2 N

( N = 0 ~ 6 )

A/D Converter Structure

A/D Converter Control Registers

ADCR0, ADCR1, ACERL, ACERH

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

verter, three or four control registers known as ADCR0,

ADCR1, ACERL and ACERH are provided. These 8-bit

registers define functions such as the selection of which

analog channel is connected to the internal A/D con-

verter, 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

ACS3~ACS0 bits in the ADCR0 register and ACS4 bit is

the ADCR1 register define the ADC input channel num-

ber. As the device contains only one actual analog to

digital converter hardware circuit, each of the individual

8 or 12 analog inputs must be routed to the converter. It

is the function of the ACS4~ACS0 bits to determine

which analog channel input pins or internal 1.25V is ac-

tually connected to the internal A/D converter.

The ACERH and ACERL control registers contain the

ACER11~ACER0 bits which determine which pins on

Port A, PE6, PE7, PF0 and PF1 are used as analog in-

puts for the A/D converter input and which pins are not

to be used as the A/D converter input. Setting the corre-

sponding bit high will select the A/D input function, clear-

ing 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.

HT66F20 Datasheet(PDF) 132 Page - Holtek Semiconductor Inc

HT66F20 Datasheet(HTML) 132 Page - Holtek Semiconductor Inc

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