Operation Mode Of 8-Bit A/D Converter - NEC mPD789101 User Manual

CHAPTER 11 8-BIT A/D CONVERTER ( µ PD789104, 789124 SUBSERIES)

11.4.3 Operation mode of 8-bit A/D converter

The 8-bit A/D converter is initially in the select mode. In this mode, A/D input selection register 0 (ADS0) is used
to select an analog input channel from ANI0 to ANI3 for A/D conversion.
A/D conversion can only be started 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 the voltage applied
to the analog input pin specified in A/D input selection 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 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 the ADM0 again
during A/D conversion, A/D conversion is completely stopped.
Rewriting ADM0
ADCS0 = 1
A/D conversion
ADCR0
INTAD0
Remarks 1. n = 0, 1, 2, 3
2. m = 0, 1, 2, 3
Figure 11-6. Software-Started A/D Conversion
ANIn ANIn
ANIn
User's Manual U13045EJ2V0UM00
Rewriting ADM0
ADCS0 = 1
ANIn ANIm
Conversion is
discontinued;
no conversion
result is preserved.
ANIn
ADCS0 = 0
ANIm
Stop
ANIm
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