C8051F52x-53x
20.2.2. Software Timer (Compare) Mode
In Software Timer mode, the PCA counter/timer value is compared to the module's 16-bit capture/compare
register (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 Cap-
ture/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
PCA
Write to
PCA0CPHn
Interrupt
ENB
1
PCA0CPMn
PCA0CN
C C C C C
P E C C M T P E
W C A A A O W C
M O P P T G M C
1 M P N n n n F
F R
C C C
F F F
2 1 0
PCA0CPLn
PCA0CPHn
6 n n n
n
n
x
0 0
0 0 x
0
1
Enable
Match
16-bit Comparator
PCA
Timebase
PCA0L
PCA0H
Figure 20.5. PCA Software Timer Mode Diagram
Rev. 0.3
203
SILICON [ SILICON ]
