NEC PD78F9488 - Manual (Page 181)

CHAPTER 10 10-BIT A/D CONVERTER
User’s Manual U15331EJ4V1UD
181
10.4.3 Operation mode of 10-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 ANI7 for A/D conversion.
A/D conversion can be started only by software, that is, by setting A/D converter mode register 0 (ADML0).
The A/D conversion result is saved to A/D conversion result register 0 (ADCRL0). 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 (ADML0) to 1 triggers A/D conversion for the 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 (ADCRL0).
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
ADML0.
If data where ADCS0 is 1 is written to ADML0 again during A/D conversion, the A/D conversion in progress is
discontinued, and a new session of A/D conversion begins for the new data.
If data where ADCS0 is 0 is written to ADML0 again during A/D conversion, A/D conversion is stopped
immediately.
Figure 10-6. Software-Started A/D Conversion
Rewriting ADML0
ADCS0 = 1 Rewriting ADML0
ADCS0 = 1
ADCS0 = 0
A/D conversion
ADCRL0
INTAD0
ANIn ANIn ANIn ANIm ANIm
Stop
ANIn ANIn ANIm
Conversion is
discontinued;
no conversion
result is preserved.
Remarks 1. n = 0 to 7
2. m = 0 to 7