UPD78F0138 NEC, UPD78F0138 Datasheet - Page 262

• Manufacturer Part Number: UPD78F0138
• Description: (UPD78xxxx) 8-Bit Single-Chip Microcontrollers
• Manufacturer: NEC

12.4.3 A/D converter operation mode
ANI7 by the analog input channel specification register (ADS) and A/D conversion is executed.
mode register (PFM).
(1) A/D conversion operation (when PFEN = 0)
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The operation mode of the A/D converter is the select mode. One channel of analog input is selected from ANI0 to
In addition, the following two functions can be selected by setting of bit 7 (PFEN) of the power-fail comparison
• Normal 10-bit A/D converter (PFEN = 0)
• Power-fail detection function (PFEN = 1)
A/D conversion
By setting bit 7 (ADCS) of the A/D converter mode register (ADM) to 1 and bit 7 (PFEN) of the power-fail
comparison mode register (PFM) to 0, the A/D conversion operation of the voltage, which is applied to the analog
input pin specified by the analog input channel specification register (ADS), is started.
When A/D conversion has been completed, the result of the A/D conversion is stored in the A/D conversion result
register (ADCR), and an interrupt request signal (INTAD) is generated. Once the A/D conversion has started and
when one A/D conversion has been completed, the next A/D conversion operation is immediately started. The
A/D conversion operations are repeated until new data is written to ADS.
If ADM, ADS, the power-fail comparison mode register (PFM), and the power-fail comparison threshold register
(PFT) are rewritten during A/D conversion, the A/D conversion operation under execution is stopped and
restarted from the beginning.
If 0 is written to ADCS during A/D conversion, A/D conversion is immediately stopped.
conversion result is undefined.
Remarks 1. n = 0 to 7
(PFEN = 0)
INTAD
ADCR
2. m = 0 to 7
Rewriting ADM
ADCS = 1
ANIn
Figure 12-10. A/D Conversion Operation
CHAPTER 12 A/D CONVERTER
User’s Manual U16228EJ2V0UD
ANIn
ANIn
Conversion is stopped
Conversion result is not retained
Rewriting ADS
ANIn
ANIn
ANIm
ANIm
ADCS = 0
ANIm
At this time, the
Stopped