HT45R38
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
a,00000001B
; disable ADC interrupt
mov
mov
mov
mov
ACSR,a
a,00100000B
ADCR,a
; setup the ACSR register to select fSYS/8 as the A/D clock
; setup ADCR register to configure Port PE0~PE3 as A/D inputs
; and select AN0 to be connected to the A/D converter
:
:
; As the Port E channel bits have changed the following START
; signal (0-1-0) must be issued within 10 instruction cycles
:
Start_conversion:
clr
set
clr
START
START
START
; reset A/D
; start A/D
Polling_EOC:
sz
EOCB
; poll the ADCR register EOCB bit to detect end of A/D conversion
; continue polling
jmp
mov
mov
mov
mov
polling_EOC
a,ADRH
adrh_buffer,a
a,ADRL
; read conversion result high byte value from the ADRH register
; save result to user defined memory
; read conversion result low byte value from the ADRL register
; save result to user defined memory
adrl_buffer,a
:
:
Start_conversion
jmp
; start next A/D conversion
Example: using Interrupt Method to detect end of conversion
; disable ADC interrupt
clr
EADI
a,00000001B
ACSR,a
mov
mov
; setup the ACSR register to select fSYS/8 as the A/D clock
mov
mov
a,00100000B
ADCR,a
:
; setup ADCR register to configure Port PE0~PE3 as A/D inputs
; and select AN0 to be connected to the A/D converter
; As the Port E channel bits have changed the following START
; signal (0-1-0) must be issued within 10 instruction cycles
:
Start_conversion:
clr
START
START
set
clr
; reset A/D
; start A/D
START
ADF
clr
; clear ADC interrupt request flag
; enable ADC interrupt
; enable global interrupt
set
set
EADI
EMI
:
:
:
; ADC interrupt service routine
ADC_ISR:
mov
mov
mov
acc_stack,a
a,STATUS
; save ACC to user defined memory
status_stack,a
:
; save STATUS to user defined memory
:
mov
mov
mov
mov
clr
a,ADRH
adrh_buffer,a
a,ADRL
adrl_buffer,a
START
START
START
:
; read conversion result high byte value from the ADRH register
; save result to user defined register
; read conversion result low byte value from the ADRL register
; save result to user defined register
set
clr
; reset A/D
; start A/D
:
Rev. 1.00
27
December 13, 2006
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
