C868 Datasheet, PDF (52/82 Pages) Infineon Technologies AG – 8-Bit Single-Chip Microcontroller

C868
A/D Converter
The C868 includes a high performance / high speed 8-bit A/D-Converter (ADC) with 5
analog input channels. It operates with a successive approximation technique and uses
self calibration mechanisms for reduction and compensation of offset and linearity errors.
The A/D converter provides the following features:
– 5 multiplexed input channels, which can also be used as digital inputs
– 8-bit resolution with TUE of +/- 2 LSB8.
– Single or continuous conversion mode
– Start of conversion by software and hardware
– Interrupt request generation after each conversion
– Using successive approximation conversion technique via a capacitor array
– Powerdown in normal, idle and slow-down modes
The ADC supports two conversion modes - single and continuous conversions. For
each mode, there are two ways in which conversion can be started - by software and by
the T13PM signal from the CCU module.
Writing a ‘0’ to bit CCU_ADEX select conversion control by ADST. Writing a ’1’ to bit
field ADST starts conversion on the channel that is specified by ADCH. In single
conversion mode, bit field ADM is cleared to ’0’. This is the default mode selected after
hardware reset. When a conversion is started, the channel specified is sampled. The
busy flag ADBSY is set and ADST is cleared. When the conversion is completed, the
interrupt request signal ADCIRQ is asserted possitively for 2 clocks and the 8-bit result
together with the number of the converted channel is transferred to the result register
ADDATH.
In continuous conversion mode, bit field ADM is set to ’1’. In this mode, the ADC
repeatedly converts the channel specified by ADCH. Bit ADST is cleared at the
beginning of the first conversion. The busy flag ADBSY is asserted until the last
conversion is completed. At the end of each conversion, the interrupt request signal
ADCIRQ will be activated. To stop conversion, ADM has to be reset by software. If the
channel number ADCH is changed while continuous conversion is in progress, the new
channel specified will be sampled in the conversions that follow.
A new request to start conversion will be allowed only after the completion of any
conversion that is in progress.
Writing a ‘1’ to bit CCU_ADEX select conversion control by T13PM trigger signal from
the CCU module.
Note: Caution must be taken when changing conversion start source. To change
conversion source from software to hardware trigger, it is best to let remaining
software conversion to complete before changing. To change conversion source
from hardware trigger to software, it is best to change source first, let any
Data Sheet
52
V 1.0, 2003-05