HT46R47-H
Bit No.
Label
Function
ACS2, ACS1, ACS0: Select A/D channel
0, 0, 0: AN0
0
1
2
ACS0
ACS1
ACS2
0, 0, 1: AN1
0, 1, 0: AN2
0, 1, 1: AN3
1, X, X: undefined, cannot be used
PCR2, PCR1, PCR0: PB3~PB0 configurations
0, 0, 0: PB3 PB2 PB1 PB0 (The ADC circuit is power off to reduce power consumption.)
0, 0, 1: PB3 PB2 PB1 AN0
3
4
5
PCR0
PCR1
PCR2
0, 1, 0: PB3 PB2 AN1 AN0
0, 1, 1: PB3 AN2 AN1 AN0
1, x, x: AN3 AN2 AN1 AN0
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,
otherwise the EOCB flag may have an undefined condition. See ²Important note for A/D ini-
tialization².
6
7
EOCB
Start the A/D conversion
START 0®1®0= Start
0®1= Reset A/D converter and set EOCB to ²1²
ADCR (22H) Register
Bit No.
Label
Function
Select the A/D converter clock source.
0, 0: fSYS/2
0
1
ADCS0
ADCS1
0, 1: fSYS/8
1, 0: fSYS/32
1, 1: Undefined
2~6
7
¾
Unused bit, read as ²0².
TEST
For internal test only.
ACSR (23H) Register
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
ACSR,a
a,00100000B
ADCR,a
; disable ADC interrupt
mov
mov
mov
mov
; setup the ACSR register to select fSYS/8 as the A/D clock
; setup ADCR register to configure Port PB0~PB3 as A/D inputs
; 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
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
; 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
jmp
mov
mov
mov
mov
polling_EOC
a,ADRH
adrh_buffer,a
a,ADRL
adrl_buffer,a
:
:
start_conversion
jmp
; start next A/D conversion
19
Rev. 1.30
March 1, 2006
HOLTEK [ HOLTEK SEMICONDUCTOR INC ]
