HT46C232 データシートの表示（PDF） - Holtek Semiconductor

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HT46C232

A/D Type 8-Bit MCU

Holtek Semiconductor 

HT46R232/HT46C232

A (7+1) bits mode PWM cycle is divided into two modu-

lation cycles (modulation cycle0~modulation cycle 1).

Each modulation cycle has 128 PWM input clock period.

In a (7+1) bits PWM function, the contents of the PWM

register is divided into two groups. Group 1 of the PWM

register is denoted by DC which is the value of

PWM.7~PWM.1. The group 2 is denoted by AC which is

the value of PWM.0.

In a (7+1) bits mode PWM cycle, the duty cycle of each

modulation cycle is shown in the table.

Parameter

Modulation cycle i

(i=0~1)

AC (0~1)

i<AC

i³AC

Duty Cycle

DC+ 1

128

DC

128

The modulation frequency, cycle frequency and cycle

duty of the PWM output signal are summarized in the

following table.

PWM

PWM Cycle PWM Cycle

Modulation Frequency Frequency Duty

fSYS/64 for (6+2) bits mode

fSYS/128 for (7+1) bits mode

fSYS/256

[PWM]/256

A/D Converter

The 8 channels and 10-bit resolution A/D converter are

implemented in this microcontroller. The reference volt-

age is VDD. The A/D converter contains 4 special regis-

ters which are; ADRL (24H), ADRH (25H), ADCR (26H)

and ACSR (27H). The ADRH and ADRL are A/D result

register higher-order byte and lower-order byte and are

read-only. After the A/D conversion is completed, the

ADRH and ADRL should be read to get the conversion

result data. The ADCR is an A/D converter control regis-

ter, which defines the A/D channel number, analog

channel select, start A/D conversion control bit and the

end of A/D conversion flag. If the users want to start an

A/D conversion, define PB configuration, select the con-

verted analog channel, and give START bit a raising

edge and falling edge (0®1®0). At the end of A/D con-

version, the EOCB bit is cleared and an A/D converter

interrupt occurs (if the A/D converter interrupt is en-

abled). The ACSR is A/D clock setting register, which is

used to select the A/D clock source.

The A/D converter control register is used to control the

A/D converter. The bit2~bit0 of the ADCR are used to

select an analog input channel. There are a total of eight

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

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

as digital I/O line decided by these 3 bits. Once a PB line

is selected as an analog input, the I/O functions and

pull-high resistor of this I/O line are disabled and the A/D

converter circuit is power 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 completed. The START

bit of the ADCR is used to begin the conversion of the

A/D converter. Giving START bit a rising edge and fall-

ing edge means that the A/D conversion has started. In

order to ensure the 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

0

ACS0

1

ACS1 Defines the analog channel select

2

ACS2

3

4

5

PCR0

PCR1

PCR2

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

power off to reduce power consumption

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

6 EOCB 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.

7 START Starts the A/D conversion. (0®1®0= start; 0®1= Reset A/D converter and set EOCB to ²1²)

ADCR (26H) Register

Rev. 1.40

19

November 23, 2005

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