MMC2107 - Freescale Semiconductor

Freescale Semiconductor, Inc.
Queued Analog-to-Digital Converter (QADC)
Register Descriptions
Table 18-9. Input Sample Times
IST[0:1]
Input Sample Times
00 Input sample time = QCLK period × 2
01 Input sample time = QCLK period × 4
10 Input sample time = QCLK period × 8
11 Input sample time = QCLK period × 16
nc...
Freescale Semiconductor, I
The programmable sample time can also be used to increase the time
interval between conversions to adjust the queue execution time or
the sampling rate.
CHAN[5:0] — Channel Number Field
The CHAN field selects the input channel number. The software
programs the channel field of the CCW with the channel number
corresponding to the analog input pin to be sampled and converted.
The analog input pin channel number assignments and the pin
definitions vary depending on whether the multiplexed or
non-multiplexed mode is used by the application. As far as the queue
scanning operations are concerned, there is no distinction between
an internally or externally multiplexed analog input.
Table 18-10 shows the channel number assignments for the
non-multiplexed mode. Table 18-11 shows the channel number
assignments for the multiplexed mode.
The channel field is programmed for channel 63 to indicate the end of
the queue. Channels 60 to 62 are special internal channels. When
one of the special channels is selected, the sampling amplifier is not
used. The value of V RL , V RH , or (V RH –V RL )/2 is placed directly onto
the converter. Also for the internal special channels, programming
any input sample time other than two has no benefit except to
lengthen the overall conversion time.
MMC2107 – Rev. 2.0
Technical Data
MOTOROLA Queued Analog-to-Digital Converter (QADC) 439
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