
Rev. 1.20
158
November 20, 2019
Rev. 1.20
159
November 20, 2019
HT66F2740
12V High Current Flash MCU
HT66F2740
12V High Current Flash MCU
• Step 9
The A/D conversion procedure can now be initialized by setting the START bit from low to high
and then low again.
• Step 10
If A/D conversion is in progress, the ADBZ flag will be set high. After the A/D conversion
process is complete, the ADBZ flag will go low and then the output data can be read from
SADOH and SADOL registers.
Note: When checking for the end of the conversion process, if the method of polling the ADBZ bit
in the SADC0 register is used, the interrupt enable step above can be omitted.
Programming Considerations
During microcontroller operations where the A/D Converter is not being used, the A/D internal
circuitry can be switched off to reduce power consumption, by clearing bit ADCEN to 0 in the
SADC0 register. When this happens, the internal A/D Converter circuits will not consume power
irrespective of what analog voltage is applied to their input lines. If the A/D Converter input lines
are used as normal I/Os, then care must be taken as if the input voltage is not at a valid logic level,
then this may lead to some increase in power consumption.
A/D Conversion Function
As the device contains a 12-bit A/D Converter, its full-scale converted digitised value is equal to
FFFH. Since the full-scale analog input value is equal to the actual A/D Converter reference voltage,
V
REF
, this gives a single bit analog input value of V
REF
divided by 4096.
1 LSB=V
REF
÷4096
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. Note that here the
V
REF
voltage is the actual A/D Converter reference voltage determined by the SAVRS field.
FFFH
FFEH
FFDH
03H
02H
01H
0
1
2
3
4093 4094 4095 4096
V
REF
4096
Analog Input Voltage
A/D Conversion
Result
1.5 LSB
0.5 LSB
Ideal A/D Transfer Function