12-Bit A / D converter
Outline
Converts an analog signal bit A / D input may be a corresponding 12-bit digital signal. A / D module has eight analog input channels. The output of the multiplexer as an input, an approximation by successive approximation. A / D module has a high-AD control register (ADCCRH), AD Control Register Low (ADCCRL), AD high number register (ADCDRH), AD lower number register (ADCDRL). ADSEL [3: 0] is provided to convert the channel selection. AD operation is performed, TRIG [2: 0] bits shall be set to 'xxx'. ADCDRH ADCDRL and contains the result of AD. AD conversion is completed, and the conversion result to ADCDRH ADCDRL, AD conversion state position '. 1', AD interrupt is generated, in AD conversion, AFLAG is bit is read as '0'.
Conversion Timing
AD conversion requires 4 steps (4 clock edges) for every conversion, clock 10 is provided an AD converter. Therefore, the need to complete the AD conversion clock 58: select at 12MHZ clock frequency fxx / 8 frequency, a clock cycle is 0.66us, each conversion requires 4 clocks, the conversion ratio is calculated as follows:
. 4 Clocks / 'bit 12 is X + bits -up time = 58 sET Clocks.
58 Clocks US = 0.66 X 38.28 MHz for 1.5 US AT (12MHz /. 8)
Note:
A / D conversion time is at least 20 us, so you have to set the transition time is greater than 20 us.
