SN8F2280 Series
USB 2.0 Full-Speed 8-Bit Micro-Controller
12 8 CHANNEL ANALOG TO DIGITAL
CONVERTER
12.1 OVERVIEW
The analog to digital converter (ADC) is SAR structure with 8-input sources and up to 4096-step resolution to transfer
analog signal into 12-bits digital data. Use CHS[2:0] bits to select analog signal input pin (AIN pin), and GCHS bit
enables global ADC channel, the analog signal inputs to the SAR ADC. The ADC resolution can be selected 8-bit and
12-bit resolutions through ADLEN bit. The ADC converting rate can be selected by ADCKS[1:0] bits to decide ADC
converting time. The ADC also builds in P4CON register to set pure analog input pin. It is necessary to set P4 as input
mode with pull-up resistor by program. After setup ADENB and ADS bits, the ADC starts to convert analog signal to
digital data. When the conversion is complete, the ADC circuit will set EOC and ADCIRQ bits to “1” and the digital data
outputs in ADB and ADR registers. If the ADCIEN = 1, the ADC interrupt request occurs and executes interrupt service
routine when ADCIRQ = 1 after ADC converting.
Note:
1. Set ADC input pin I/O direction as input mode without pull-up resistor.
2. Disable ADC (set ADENB = “0”) before enter power down (sleep) mode to save power consumption.
3. Set related bit of P4CON register to avoid extra power consumption in power down mode.
4. Delay 100uS after enable ADC (set ADENB = “1”) to wait ADC circuit ready for conversion.
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