HT46RB70 datasheet(21/53 Pages) HOLTEK

21 / 53 page

HT46RB70

Rev. 1.10

November 1, 2006

The following two programming examples illustrate how to setup and implement an A/D conversion. In the first exam-

ple, the method of polling the EOCB bit in the ADCR register is used to detect when the conversion cycle is complete,

whereas in the second example, the A/D interrupt is used to determine when the conversion is complete.

Example: using EOCB Polling Method to detect end of conversion

clr

EADI

; disable ADC interrupt

mov

a,00000001B

mov

ACSR,a

; setup the ACSR register to select fSYS/8 as the A/D clock

mov

a,00100000B

; setup ADCR register to configure Port PB0~PB3 as A/D inputs

mov

ADCR,a

; and select AN0 to be connected to the A/D converter

; As the Port B channel bits have changed the following START

; signal (0-1-0) must be issued within 10 instruction cycles

Start_conversion:

clr

START

set

START

; reset A/D

clr

START

; start A/D

Polling_EOC:

EOCB

; poll the ADCR register EOCB bit to detect end of A/D conversion

jmp

polling_EOC

; continue polling

mov

a,ADRH

; read conversion result high byte value from the ADRH register

mov

adrh_buffer,a

; save result to user defined memory

mov

a,ADRL

; read conversion result low byte value from the ADRL register

mov

adrl_buffer,a

; save result to user defined memory

jmp

Start_conversion

; start next A/D conversion

Example: using Interrupt Method to detect end of conversion

clr

EADI

; disable ADC interrupt

mov

a,00000001B

mov

ACSR,a

; setup the ACSR register to select fSYS/8 as the A/D clock

mov

a,00100000B

; setup ADCR register to configure Port PB0~PB3 as A/D inputs

mov

ADCR,a

; and select AN0 to be connected to the A/D converter

; As the Port B channel bits have changed the following START

; signal (0-1-0) must be issued within 10 instruction cycles

Start_conversion:

clr

START

set

START

; reset A/D

clr

START

; start A/D

clr

ADF

; clear ADC interrupt request flag

set

EADI

; enable ADC interrupt

set

EMI

; enable global interrupt

; ADC interrupt service routine

ADC_ISR:

mov

acc_stack,a

; save ACC to user defined memory

mov

a,STATUS

mov

status_stack,a

; save STATUS to user defined memory

mov

a,ADRH

; read conversion result high byte value from the ADRH register

mov

adrh_buffer,a

; save result to user defined register

mov

a,ADRL

; read conversion result low byte value from the ADRL register

mov

adrl_buffer,a

; save result to user defined register

clr

START

set

START

; reset A/D

clr

START

; start A/D

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