HT46R24/HT46C24

Rev. 1.50

21

May 3, 2004

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 INTC1.0

; disable A/D interrupt in interrupt control register

mov a,00100000B

mov ADCR,a

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

; AN0 to be connected to the A/D converter

mov a,00000001B

mov ACSR,a

Start_conversion:

clr ADCR.7

set ADCR.7

; reset A/D

clr ADCR.7

; start A/D

Polling_EOC:

sz ADCR.6

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

jmp polling_EOC

; continue polling

mov a,ADRH

; read conversion result from the high byte ADRH register

mov adrh_buffer,a

; save result to user defined register

mov a,ADRL

; read conversion result from the low byte ADRL register

mov adrl_buffer,a

; save result to user defined register

:

:

jmp start_conversion

; start next A/D conversion

Example: using Interrupt method to detect end of conversion

set INTC0.0

; interrupt global enable

set INTC1.0

; enable A/D interrupt in interrupt control register

mov a,00100000B

mov ADCR,a

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

; AN0 to be connected to the A/D converter

mov a,00000001B

mov ACSR,a

start_conversion:

clr ADCR.7

set ADCR.7

; reset A/D

clr ADCR.7

; start A/D

:

:

; interrupt service routine

EOC_service routine:

mov a_buffer,a

; save ACC to user defined register

mov a,ADRH

; read conversion result from the high byte ADRH register

mov adrh_buffer,a

; save result to user defined register

mov a,ADRL

; read conversion result from the low byte ADRL register

mov adrl_buffer,a

; save result to user defined register

clr ADCR.7

set ADCR.7

; reset A/D

clr ADCR.7

; start A/D

mov a,a_buffer

; restore ACC from temporary storage

reti