Holtek BS66F340 - A;D Programming Examples

Rev. 1.60 154 August 20, 2019 Rev. 1.60 155 August 20, 2019
BS66F340/BS66F350/BS66F360/BS66F370
Touch A/D Flash MCU with LED Driver
BS66F340/BS66F350/BS66F360/BS66F370
Touch A/D Flash MCU with LED Driver
The A/D Converter input voltage value can be calculated using the following equation:
A/D input voltage = A/D output digital value × V
REF
÷ 4096
The diagram shows the ideal transfer function between the analog input value and the digitised
output value for the A/D converter. Except for the digitised zero value, the subsequent digitised
values will change at a point 0.5 LSB below where they would change without the offset, and the
last full scale digitised value will change at a point 1.5 LSB below the V
REF
level.

 









 



   
 



Ideal A/D Transfer Function
A/D Programming Examples
The following two programming examples illustrate how to setup and implement an A/D
conversion. In the rst example, the method of polling the ADBZ 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 an ADBZ polling method to detect the end of conversion
clr ADE ; disable ADC interrupt
set VREFP_EXT ; deselect the temperature sensor reference voltage
mov a,03H ; select f
SYS
/8 as A/D clock and A/D internal power supply
mov ADCR1,a ; as reference voltage
set ADCEN
mov a,03H ; setup PBS0 to congure pin AN0
mov PBS0,a
mov a,20H
mov ADCR0,a ; enable and connect AN0 channel to A/D converter
:
start_conversion:
clr START ; high pulse on start bit to initiate conversion
set START ; reset A/D
clr START ; start A/D
:
polling_EOC:
sz ADBZ ; poll the ADCR0 register ADBZ bit to detect end of A/D conversion
jmp polling_EOC ; continue polling
:
mov a,ADRL ; read low byte conversion result value
mov ADRL_buffer,a ; save result to user dened register
mov a,ADRH ; read high byte conversion result value
mov ADRH_buffer,a ; save result to user dened register
:
jmp start_conversion ; start next A/D conversion