C8051F02X Datasheet, PDF (253/272 Pages) Silicon Laboratories – 8K ISP FLASH MCU Family

C8051F020/1/2/3
23.2.1. Edge-triggered Capture Mode
In this mode, a valid transition on the CEXn pin causes PCA0 to capture the value of the PCA0 counter/timer and
load it into the corresponding module's 16-bit capture/compare register (PCA0CPLn and PCA0CPHn). The CAPPn
and CAPNn bits in the PCA0CPMn register are used to select the type of transition that triggers the capture: low-to-
high transition (positive edge), high-to-low transition (negative edge), or either transition (positive or negative edge).
When a capture 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 vec-
tors to the interrupt service routine, and must be cleared by software.
Figure 23.4. PCA Capture Mode Diagram
PCA0CPMn
P ECCMT P E
WCA A AOWC
MOP P TGMC
1 MPN n n n F
6nnn
n
n
PCA Interrupt
PCA0CN
CC CCCCC
FR CCCCC
FFFFF
43210
Port I/O
Crossbar ^CEXn
0
1
0
1
PCA0CPLn PCA0CPHn
Capture
PCA
Timebase
PCA0L
PCA0H
Note: The CEXn input signal must remain high or low for at least 2 system clock cycles in order to be valid.
Rev. 1.4
253