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Rev. 1.00
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Standard 8051 8-Bit Flash MCU
HT85F2260/HT85F2270/HT85F2280
Digital to
Analog Converter – DAC
DAC Reference Voltage Source
The DAC can obtain its reference voltage from three different sources, the VCCA2 power supply
pin, an externally supplied reference voltage supplied on pin VREF or from the internal voltage
reference generator. Two bits control which reference source is selected, these are the VREFIS and
VREFDS bits.
DAC Converter Voltage Reference Select
VREFIS
VREFDS
Reference Source
0
0
VCCA� pin
0
1
Exte�nall� s�pplied on VREF pin
1
0
VCCA� pin
1
1
Inte�nal Voltage Refe�ence Gene�ato�
Programming Considerations
Note that data written to the two DAC registers must be implemented in a specific way. Any
data written into the DAH register will load both the data into the DAL and DAH registers
simultaneously and influence the DAC output at the same time. However writing data to the DAL
register will only place the data into a low byte buffer and not directly into the DAL register. For
this reason, writing data to the DAL register should be followed by a write instruction to the DAH
register.