XC164-16 Datasheet, PDF (95/417 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller with C166SV2 Core Volume 2 (of 2): Peripheral Units

XC164-16 Derivatives
Peripheral Units (Vol. 2 of 2)
The Analog/Digital Converter
16.2.3 Wait for Read Mode
If in default mode of the ADC a previous conversion result has not been read out of the
result register by the time a new conversion is complete, the previous result is lost
because it is overwritten by the new value, and the A/D overrun error interrupt request
flag ADEIR will be set.
In order to avoid error interrupts and the loss of conversion results especially when using
continuous conversion modes, the ADC can be switched to “Wait for Read Mode” by
setting bit ADWR.
If the result value has not been read by the time the current conversion is complete, the
new result is stored in a temporary buffer and the next conversion is suspended (ADST
and ADBSY will remain set in the meantime, but no end-of-conversion interrupt will be
generated). After reading the previous value the temporary buffer is copied into
ADC_DAT (generating an ADCIR interrupt) and the suspended conversion is started.
This mechanism applies to both single and continuous conversion modes.
Note: While in standard mode continuous conversions are executed at a fixed rate
(determined by the conversion time), in “Wait for Read Mode” there may be delays
due to suspended conversions. However, this only affects the conversions, if the
CPU (or PEC) cannot keep track with the conversion rate.
Conversion
of Channel..
#3
#2
#1
wait
#0
#3
Write ADC_DAT
ADC_DAT Full
Temp-Latch Full
Generate Interrupt
Request
Read of ADC_DAT;
Result of Channel:
#x
#3
#2
#1
1
Hold Result in
Temp-Latch
#0
#3
#x
#3
#2
#1
#0
MC_ADC0002_WAITREAD
Figure 16-4 Wait for Read Mode Example
User’s Manual
ADC_X41, V2.1
16-13
V2.1, 2004-03