Rev. 1.10
138
October 23, 2020
Rev. 1.10
139
October 23, 2020
BC66F5652
2.4GHz RF Transceiver A/D Flash MCU
BC66F5652
2.4GHz RF Transceiver A/D Flash MCU
• Step 9
The A/D conversion procedure can now be initialised 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 completed, the ADBZ flag will go low and then output data can be read from the
SADOH and SADOL registers. If the ADC interrupt is enabled and the stack is not full, data can
be acquired by interrupt service program.
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 conversion
internal circuitry can be switched off to reduce power consumption by setting the ADCEN bit low
in the SADC0 register. When this happens, the internal A/D conversion 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 converter input voltage = A/D converter 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 bit 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 Conversion Function