The "windowing mode" is enabled by setting CR1[WE]. When set, the comparator output
is sampled only when WINDOW=1. This feature can be used to ignore the comparator
output during time periods in which the input voltages are not valid. This is especially
useful when implementing zero-crossing-detection for certain PWM applications.
The comparator filter and sampling features can be combined as shown in the following
table. Individual modes are discussed below.
Table 29-15. Comparator sample/filter controls
Mode # CR1[EN] CR1[WE] CR1[SE]
CR0[FILTER_C
NT]
FPR[FILT_PER] Operation
1 0 X X X X Disabled
See the Disabled mode (# 1).
2A 1 0 0 0x00 X Continuous Mode
See the Continuous mode (#s 2A &
2B).
2B 1 0 0 X 0x00
3A 1 0 1 0x01 X Sampled, Non-Filtered mode
See the Sampled, Non-Filtered
mode (#s 3A & 3B).
3B 1 0 0 0x01 > 0x00
4A 1 0 1 > 0x01 X Sampled, Filtered mode
See the Sampled, Filtered mode (#s
4A & 4B).
4B 1 0 0 > 0x01 > 0x00
5A 1 1 0 0x00 X Windowed mode
Comparator output is sampled on
every rising bus clock edge when
SAMPLE=1 to generate COUTA.
See the Windowed mode (#s 5A &
5B).
5B 1 1 0 X 0x00
6 1 1 0 0x01 0x01–0xFF Windowed/Resampled mode
Comparator output is sampled on
every rising bus clock edge when
SAMPLE=1 to generate COUTA,
which is then resampled on an
interval determined by FILT_PER to
generate COUT.
See the Windowed/Resampled
mode (# 6).
7 1 1 0 > 0x01 0x01–0xFF Windowed/Filtered mode
Comparator output is sampled on
every rising bus clock edge when
SAMPLE=1 to generate COUTA,
which is then resampled and filtered
to generate COUT.
See the Windowed/Filtered mode
(#7).
All other combinations of CR1[EN], CR1[WE], CR1[SE], CR0[FILTER_CNT], and FPR[FILT_PER] are illegal.
Chapter 29 Comparator (CMP)
KL25 Sub-Family Reference Manual, Rev. 3, September 2012
Freescale Semiconductor, Inc. 521
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