C508_01 Datasheet, PDF (187/267 Pages) Infineon Technologies AG – 8-Bit CMOS Microcontroller

C508
On-Chip Peripheral Components
6.5
A/D Converter
The C508 includes a high performance / high speed 10-bit A/D Converter (ADC) with
8 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:
– 8 input channels (Port 4), which can also be used as digital inputs
– 10-bit resolution
– Single or continuous conversion mode
– Internal start-of-conversion trigger capability
– Interrupt request generation after each conversion
– Using successive approximation conversion technique via a capacitor array
– Built-in hidden calibration of offset and linearity errors
The externally applied reference voltages must be held at a fixed value within the
specifications. The main functional blocks of the A/D Converter are shown in
Figure 6-49.
6.5.1 A/D Converter Operation
An internal start of a single A/D conversion is triggered by a write-to-ADDATL instruction.
The start procedure itself is independent of the value which is written to ADDATL. When
single conversion mode is selected (bit ADM = 0) only one A/D conversion is performed.
In continuous mode (bit ADM = 1), a new A/D conversion is triggered automatically upon
completion of a previous conversion, until bit ADM is reset.
The busy flag BSY (ADCON0.4) is automatically set when an A/D conversion is in
progress. After completion of the conversion, it is reset by hardware. This flag is read
only; a write has no effect. The interrupt request flag IADC (IRCON.0) is set when an A/
D conversion is completed.
The bits MX0 to MX2 in special function register ADCON0 and ADCON1 are used for
selection of the analog input channel. The bits MX0 to MX2 are represented in both
registers ADCON0 and ADCON1; however these bits are present only once. Therefore,
there are two methods of selecting an analog input channel. If a new channel is selected
in ADCON1, the change is automatically done in the corresponding bits MX0 to MX2 in
ADCON0; and vice versa.
Port 4 is an input port. These pins can be used either for digital input functions or as the
analog inputs of the A/D Converter. If less than 8 analog inputs are required, the unused
inputs are free for digital input functions. Any unused inputs should be connected to
V_SSA.
User’s Manual
6-122
2001-05