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Scan IF Operation
24-9Scan IF
Direct Analog And Digital Inputs
By setting the SIFCAX bit, external analog or digital signals can be connected
directly to the comparator through the SIFCIx inputs. This allows
measurement capabilities for optical encoders and other sensors.
Comparator Input Selection And Output Bit Selection
The SIFCAX and SIFSH bits select between the SIFCIx channels and the
SIFCHx channels for the comparator input as described in Table 24−1.
Table 24−1.SIFCAX and SIFSH Input Selection
SIFCAX SIFSH Operation
0 0 SIFCHx and excitation circuitry is selected
0 1 SIFCHx and sample-and-hold circuitry is selected
1 X SIFCIx inputs are selected
The TESTDX signal and SIFTESTS1(tsm) signal select between the
SIFxOUT output bits and the SIFTCHxOUT output bits for the comparator
output as described in Table 24−2. TESTDX is controlled by the SIFTESTD bit.
Table 24−2.Selected Output Bits
TESTDX SIFCH(tsm) SIFTESTS1(tsm) Selected Output Bit
0 00 X SIF0OUT
0 01 X SIF1OUT
0 10 X SIF2OUT
0 11 X SIF3OUT
1 X 0 SIFTCH0OUT
1 X 1 SIFTCH1OUT
When TESTDX = 0, the SIFCHx(tsm) signals select which SIFCIx or SIFCHx
channel is excited and connected to the comparator. The SIFCHx(tsm) signals
also select the corresponding output bit for the comparator result.
When TESTDX = 1, channel selection depends on the SIFTESTS1(tsm)
signal. When TESTDX = 1 and SIFTESTS1(tsm) = 0, input channel selection
is controlled with the SIFTCH0x bits and the output bit is SIFTCH0OUT. When
TESTDX = 1 and SIFTESTS1(tsm) = 1, input channel selection is controlled
with the SIFTCH1x bits and the output bit is SIFTCH1OUT.