CHAPTER 10 8-BIT A/D CONVERTER (µPD789426 AND 789446 SUBSERIES)
10.4.3 Operation mode of 8-bit A/D converter
The A/D converter is initially in select mode. In this mode, analog input channel specification register 0 (ADS0) is
used to select an analog input channel from ANI0 to ANI5 for A/D conversion.
A/D conversion can be started only by software, that is, by setting A/D converter mode register 0 (ADM0).
The A/D conversion result is saved to A/D conversion result register 0 (ADCR0). At the same time, an interrupt
request signal (INTAD0) is generated.
• Software-started A/D conversion
Setting bit 7 (ADCS0) of A/D converter mode register 0 (ADM0) to 1 triggers A/D conversion for a voltage
applied to the analog input pin specified in analog input channel specification register 0 (ADS0). Upon
completion of A/D conversion, the conversion result is saved to A/D conversion result register 0 (ADCR0). At
the same time, an interrupt request signal (INTAD0) is generated. Once A/D conversion is activated, and
completed, another session of A/D conversion is started. A/D conversion is repeated until new data is written
to ADM0. If data where ADCS0 is 1 is written to ADM0 again during A/D conversion, the ongoing session of
A/D conversion is discontinued, and a new session of A/D conversion begins for the new data. If data where
ADCS0 is 0 is written to ADM0 again during A/D conversion, A/D conversion is stopped immediately.
Figure 10-6. Software-Started A/D Conversion
Rewriting ADM0
ADCS0 = 1
Rewriting ADM0
ADCS0 = 1
ADCS0 = 0
A/D conversion
ANIn
ANIn
ANIn
ANIm
ANIm
Conversion is
discontinued;
no conversion
Stop
result is preserved.
ADCR0
INTAD0
ANIn
ANIn
ANIm
Remarks 1. n = 0 to 5
2. m = 0 to 5
User’s Manual U15075EJ1V0UM00
191
NEC [ NEC ]
