C8051F85X86X Datasheet, PDF (145/290 Pages) Silicon Laboratories – Low-Cost 8-bit MCU Family with up to 8 kB of Flash

C8051F85x/86x
20.3.3. 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. An interrupt request is generated if the CCFn interrupt for that module is 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.
PCA0CPLn PCA0CPHn
ECOMn
(Compare Enable)
16-bit Comparator
MATn (Match Enable)
match
CCFn
(Interrupt Flag)
PCA Clock
PCA0L
PCA0H
Figure 20.3. PCA Software Timer Mode Diagram
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Preliminary Rev 0.6