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C8051F120/1/2/3/4/5/6/7 C8051F130/1/2/3
24.2.2. Software Timer (Compare) Mode
In Software Timer mode, the PCA0 counter/timer is compared to the module's 16-bit capture/compare reg-
ister (PCA0CPHn and PCA0CPLn). When a match occurs, the Capture/Compare Flag (CCFn) in PCA0CN
is set to logic 1 and an interrupt request is generated if CCF interrupts are enabled. The CCFn bit is not
automatically cleared by hardware when the CPU vectors to the interrupt service routine, and must be
cleared by software. Setting the ECOMn and MATn bits in the PCA0CPMn register enables Software
Timer mode.
Important Note About Capture/Compare Registers : When writing a 16-bit value to the PCA0 Capture/
Compare registers, the low byte should always be written first. Writing to PCA0CPLn clears the ECOMn bit
to '0'; writing to PCA0CPHn sets ECOMn to '1'.
Write to
0
PCA0CPLn
ENB
Reset
Write to
PCA0CPHn
ENB
1
Figure 24.5. PCA Software Timer Mode Diagram
330
PCA0CPMn
P
P
E
C
C
M
T
E
W
W
C
A
A
A
O
C
M
M
O
P
P
T
G
C
1
n
M
P
N
n
n
F
6
n
n
n
n
n
x
0 0
0 0
x
Enable
PCA
Timebase
Rev. 1.4
PCA0CPLn
PCA0CPHn
16-bit Comparator
PCA0L
PCA0H
PCA
Interrupt
PCA0CN
C
C
C
C
C
C
C
C
F
R
C
C
C
C
C
C
F
F
F
F
F
F
5
4
3
2
1
0
0
Match
1
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