Datasheet

Analog-to-Digital Converter
Technical Data MC68HC912DT128A — Rev 4.0
386 Analog-to-Digital Converter MOTOROLA
mode is required, the existing continuous sequence must be
interrupted, the control registers modified, and a new conversion
sequence initiated.
MULT — Multi-Channel Sample Mode
0 = Sample only the specified channel
1 = Sample across many channels
When MULT is 0, the ATD sequence controller samples only from the
specified analog input channel for an entire conversion sequence.
The analog channel is selected by channel selection code (control
bits CC/CB/CA located in ATDCTL5).
When MULT is 1, the ATD sequence controller samples across
channels. The number of channels sampled is determined by the
sequence length value (S8C, S1C control bits). The first analog
channel examined is determined by channel selection code (CC, CB,
CA control bits); subsequent channels sampled in the sequence are
determined by incrementing the channel selection code.
SC — Special Channel Conversion Mode
0 = Perform A/D conversion on an analog input channel
1 = Perform special channel A/D conversion
SC determines if the ATD module performs A/D conversions on any
of the analog input channels (normal operation) or whether it performs
a conversion on one of the defined, special channels. The special
channels are normally used to test the A/D machine and include
converting the high and low reference potentials for the module. The
control bits CC/CB/CA are used to indicate which special channel is
to be converted.
Table 19-8. Special Channel Conversion Select Coding
CC CB CA Special Expected
Channel Digital Result Code
0XX reserved –
100 VRH $FF
1 0 1 VRL $00
1 1 0 (VRH + VRL)/2 $7F
111 reserved –
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cale Semiconductor,
I
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