Datasheet

 2012 Microchip Technology Inc. DS30575A-page 473
PIC18F97J94 FAMILY
FIGURE 22-13: INSIDE WINDOW COMPARISON OPERATION
22.7.5.3 Outside Window Comparison
When the Compare Mode bits CM<1:0> are
programmed as '11', the converter compares the
sampled value to see if it falls outside of the threshold
values in the buffer and mirrored channel location.
Again, since the value in the mirrored channel location
is always the greater value of the two thresholds, the
condition is met when either:
Converted Value >Threshold 2
or
Threshold 1 > Converted Value
In these cases, the following occurs:
• The Compare Hit bit (CHHn) for the correspond-
ing channel is set.
• If the converted value is greater than Threshold
2, the CHHn bit for the mirrored channel is also
set. If it is less than Threshold 1, the mirrored
channel bit remains '0'.
• If the Write Mode bits, WM<1:0>
(ADCON5L<3:2>), are programmed to '01':
- If the converted value is above Threshold 2,
the converted value is written to the mirrored
channel address, replacing the upper thresh-
old value.
- If the converted value is below Threshold 1,
the converted value is written to the channel
address, replacing the lower threshold value.
• If WM<1:0> = 10, the converted value is
discarded.
The changes to the result buffer and the Compare Hit
register are shown in Figure 22-15 (over the upper
threshold) and Figure 22-16 (under the lower thresh-
old).
Note that when a Windowed Comparison mode is
selected and channel mirroring is enabled, nothing pre-
vents a conversion from another operation from being
stored in the mirrored channel location. In the previous
examples of windowed operation, if AN10 is included in
a Threshold Detect operation, a conversion on AN10
might be tested against the upper threshold for AN2,
stored in that location. This could result in the threshold
value being overwritten and/or the CHH10 bit being set.
ADC1BUF15 —
ADC1BUF14 —
ADC1BUF13 —
ADC1BUF12 —
ADC1BUF11 —
ADC1BUF10 Threshold 2
ADC1BUF9 —
ADC1BUF8 —
ADC1BUF7 —
ADC1BUF6 —
ADC1BUF5 —
ADC1BUF4 —
ADC1BUF3 —
ADC1BUF2 Threshold 1
ADC1BUF1 —
ADC1BUF0 —
Before Conversion and Comparison
AD1CHITL
15 14 13 12 11 10 9 8
00000000
765432 10
000001 00
After Conversion and Comparison
Compare Only
(‘10’)
Compare and
Store (‘01’)
ADC1BUF15 — —
ADC1BUF14 — —
ADC1BUF13 — —
ADC1BUF12 — —
ADC1BUF11 — —
ADC1BUF10 Threshold 2 Threshold 2
ADC1BUF9 — —
ADC1BUF8 — —
ADC1BUF7 — —
ADC1BUF6 — —
ADC1BUF5 — —
ADC1BUF4 — —
ADC1BUF3 — —
ADC1BUF2 Threshold 1 Conversion Value
ADC1BUF1 — —
ADC1BUF0 — —
AD1CHITL
15 14 13 12 11 10 9 8
00000000
76543210
00000000