PIC16F688
7.8
Comparator C2 Gating Timer1
7.9
Synchronizing Comparator C2
Output to Timer1
This feature can be used to time the duration or interval
of analog events. Clearing the T1GSS bit of the
CMCON1 register will enable Timer1 to increment
based on the output of Comparator C2. This requires
that Timer1 is on and gating is enabled. See
Section 6.0 “Timer1 Module with Gate Control” for
details.
The output of Comparator C2 can be synchronized with
Timer1 by setting the C2SYNC bit of the CMCON1
register. When enabled, the comparator output is
latched on the falling edge of the Timer1 clock source.
If a prescaler is used with Timer1, the comparator
output is latched after the prescaling function. To
prevent a race condition, the comparator output is
latched on the falling edge of the Timer1 clock source
and Timer1 increments on the rising edge of its clock
source. Reference the comparator block diagrams
(Figure 7-2 and Figure 7-3) and the Timer1 Block
Diagram (Figure 6-1) for more information.
It is recommended to synchronize Comparator C2 with
Timer1 by setting the C2SYNC bit when the comparator
is used as the Timer1 gate source. This ensures Timer1
does not miss an increment if the comparator changes
during an increment.
REGISTER 7-2:
CMCON1: COMPARATOR CONFIGURATION REGISTER
U-0
—
U-0
—
U-0
—
U-0
—
U-0
—
U-0
—
R/W-1
R/W-0
T1GSS
C2SYNC
bit 7
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
bit 7-2
bit 1
Unimplemented: Read as ‘0’
T1GSS: Timer1 Gate Source Select bit(1)
1= Timer1 gate source is T1G pin (pin should be configured as digital input)
0= Timer1 gate source is Comparator C2 output
bit 0
C2SYNC: Comparator C2 Output Synchronization bit(2)
1= Output is synchronized with falling edge of Timer1 clock
0= Output is asynchronous
Note 1: Refer to Section 6.6 “Timer1 Gate”.
2: Refer to Figure 7-3.
DS41203D-page 62
© 2007 Microchip Technology Inc.
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