NEC mPD789101, User Manual

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CHAPTER 12 10-BIT A/D CONVERTER (
µ
PD789114, 789134 SUBSERIES)
User’s Manual U13045EJ2V0UM00
157
12.4.3 Operation mode of 10-bit A/D converter
The 10-bit A/D converter is initially in the select mode. In this mode, A/D input select register 0 (ADS0) is used
to select an analog input channel from ANI0 to ANI3 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) triggers A/D conversion for a voltage applied
to the analog input pin specified in A/D input select 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, 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 the 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 completely stopped.
Figure 12-6. Software-Started A/D Conversion
Remarks 1. n = 0, 1, 2, 3
2. m = 0, 1, 2, 3
Rewriting ADM0
ADCS0 = 1 Rewriting ADM0
ADCS0 = 1
ADCS0 = 0
A/D conversion
ADCR0
INTAD0
ANIn ANIn ANIn ANIm ANIm
Stop
ANIn ANIn ANIm
Conversion is
discontinued;
no conversion
result is preserved.