C8051T620/1/6/7 & C8051T320/1/2/3
270
Rev. 1.2
Figure 29.2. PCA Counter/Timer Block Diagram
29.2. PCA0 Interrupt Sources
Figure 29.3 shows a diagram of the PCA interrupt tree. There are five independent event flags that can be
used to generate a PCA0 interrupt. They are: the main PCA counter overflow flag (CF), which is set upon
a 16-bit overflow of the PCA0 counter, an intermediate overflow flag (COVF), which can be set on an over-
flow from the 8th, 9th, 10th, or 11th bit of the PCA0 counter, and the individual flags for each PCA channel
(CCF0, CCF1, CCF2, CCF3, and CCF4), which are set according to the operation mode of that module.
These event flags are always set when the trigger condition occurs. Each of these flags can be individually
selected to generate a PCA0 interrupt, using the corresponding interrupt enable flag (ECF for CF, ECOV
for COVF, and ECCFn for each CCFn). PCA0 interrupts must be globally enabled before any individual
interrupt sources are recognized by the processor. PCA0 interrupts are globally enabled by setting the EA
bit and the EPCA0 bit to logic 1.
PCA0CN
C
F
C
R
C
C
F
0
C
C
F
2
C
C
F
1
C
C
F
4
C
C
F
3
PCA0MD
C
I
D
L
W
D
T
E
E
C
F
C
P
S
1
C
P
S
0
W
D
L
C
K
C
P
S
2
IDLE
0
1
PCA0H
PCA0L
Snapshot
Register
To SFR Bus
Overflow
To PCA Interrupt System
CF
PCA0L
read
To PCA Modules
SYSCLK/12
SYSCLK/4
Timer 0 Overflow
ECI
000
001
010
011
100
101
SYSCLK
External Clock/8