Rainbow Electronics AT90C8534 - Manual (Page 33)

AT90C8534
33
Figure 33. ADC Timing Diagram, Free Run Conversion
ADC Noise Canceler Function
The ADC features a noise canceler that enables conversion during idle mode to reduce noise induced from the CPU core.
To make use of this feature, the following procedure should be used.
1. Make sure that the ADC is enabled and is not busy converting. Single Conversion Mode must be selected and the
ADC conversion complete interrupt must be enabled. Thus:
ADEN = 1
ADSC = 0
ADFR = 0
ADIE = 1
2. Enter idle mode. The ADC will start a conversion once the CPU has been halted.
3. If no other interrupts occur before the ADC conversion completes, the ADC interrupt will wake up the MCU and
execute the ADC conversion complete interrupt routine.
Table 6. ADC Conversion Time
Condition
Sample Cycle
Number
Result Ready
(Cycle Number)
Total Conversion
Time (Cycles)
Total Conversion
Time (µs)
1st Conversion, Free Run 14 25 25 147 - 313
1st Conversion, Single 14 25 26 153 - 325
Free Run Conversion 2 13 13 76 - 163
Single Conversion 2 13 14 82 - 175
11 12 13
MSB of result
LSB of result
ADC clock
ADSC
Hold strobe
ADIF
ADCH
ADCL
Cycle number
1 2
One Conversion Next
Conversion