16-Bit Pulse Width Modulator Mode; Figure 24.9. Pca 16-Bit Pwm Mode - Silicon Laboratories C8051F12 Series Manual

C8051F120/1/2/3/4/5/6/7 C8051F130/1/2/3

24.2.6. 16-Bit Pulse Width Modulator Mode

Each PCA0 module may also be operated in 16-Bit PWM mode. In this mode, the 16-bit capture/compare
module defines the number of PCA0 clocks for the low time of the PWM signal. When the PCA0 counter
matches the module contents, the output on CEXn is asserted high; when the counter overflows, CEXn is
asserted low. To output a varying duty cycle, new value writes should be synchronized with PCA0 CCFn
match interrupts. 16-Bit PWM Mode is enabled by setting the ECOMn, PWMn, and PWM16n bits in the
PCA0CPMn register. For a varying duty cycle, CCFn should also be set to logic 1 to enable match inter-
rupts. The duty cycle for 16-Bit PWM Mode is given by Equation 24.3.
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'.
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
1 0 0 0 0 0
Enable
PCA Timebase
334
Equation 24.3. 16-Bit PWM Duty Cycle
(
65536 PCA0CPn
---------------------------------------------------- -
DutyCycle =
PCA0CPHn PCA0CPLn
16-bit Comparator
PCA0H PCA0L
Overflow

Figure 24.9. PCA 16-Bit PWM Mode

Rev. 1.4
)
–
65536
match CEXn
SET
S Q Crossbar
R Q
CLR
Port I/O