HT46R12 datasheet(21/45 Pages) HOLTEK

21 / 45 page

HT46R12

Rev. 1.00

November 1, 2005

channels to select. The bit5~bit3 of the ADCR are used

to set the PB configurations. PB can be an analog input

or as digital I/O line determined by these 3 bits.

PCR2 PCR1 PCR0

3210

PB3

PB2

PB1

PB0

PB3

PB2

PB1

AN0

PB3

PB2

AN1

AN0

PB3

AN2

AN1

AN0

AN3

AN2

AN1

AN0

Port B Configuration

Once a PB line is selected as an analog input, the I/O

functions and pull-high resistor of this I/O line are dis-

abled and the A/D converter circuit is powered on. The

EOCB bit (bit6 of the ADCR) is end of A/D conversion

flag. Check this bit to know when A/D conversion is com-

pleted. The START bit of the ADCR is used to begin the

conversion of the A/D converter. Giving START bit a ris-

ing edge and falling edge means that the A/D conver-

sion has started. In order to ensure that A/D conversion

is completed, the START should remain at

²0² until the

EOCB is cleared to

²0² (end of A/D conversion).

Bit 7 of the ACSR register is used for test purposes only

and must not be used for other purposes by the applica-

tion program. Bit1 and bit0 of the ACSR register are

used to select the A/D clock source.

When the A/D conversion has completed, the A/D inter-

rupt request flag will be set. The EOCB bit is set to

²1²

when the START bit is set from

²0² to ²1².

Important Note for A/D initialization:

Special care must be taken to initialize the A/D con-

verter each time the Port B A/D channel selection bits

are modified, otherwise the EOCB flag may be in an un-

defined condition. An A/D initialization is implemented

by setting the START bit high and then clearing it to zero

within 10 instruction cycles of the Port B channel selec-

tion bits being modified. Note that if the Port B channel

selection bits are all cleared to zero then an A/D initial-

ization is not required.

Bit No.

Label

Function

ADCS0

ADCS1

Selects the A/D converter clock source

00=system clock/2

01=system clock/8

10=system clock/32

11=undefined

2~6

Unused bit, read as

²0²

TEST

For test mode used only

ACSR (27H) Register

Bit No.

Label

Function

ACS0

ACS1

ACS2

ACS2, ACS1, ACS0: Select A/D channel

0, 0, 0: AN0

0, 0, 1: AN1

0, 1, 0: AN2

0, 1, 1: AN3

1, x, x: Undefined, cannot be used

PCR0

PCR1

PCR2

Defines the port B configuration select. If PCR0, PCR1 and PCR2 are all zero, the ADC circuit is

powered off to reduce power consumption

EOCB

Indicates end of A/D conversion. (0 = end of A/D conversion)

Each time bits 3~5 change state the A/D should be initialized by issuing a START signal, other-

wise the EOCB flag may have an undefined condition. See

²Important note for A/D initialization².

START Starts the A/D conversion. (0

®1®0= start; 0®1= Reset A/D converter and set EOCB to ²1²)

ADCR (26H) Register

Bit7

Bit6

Bit5

Bit4

Bit3

Bit2

Bit1

Bit0

ADRL (24H)

¾¾¾¾¾¾¾

ADRH (25H)

Note:

D0~D8 is A/D conversion result data bit LSB~MSB.

ADRL (24H), ADRH (25H) Register

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