C8051F303-GSR Silicon Labs, C8051F303-GSR Datasheet - Page 163

• Manufacturer Part Number: C8051F303-GSR
• Description: 8-bit Microcontrollers - MCU 8KB 14Pin MCU
• Manufacturer: Silicon Labs

Specifications of C8051F303-GSR

• Rohs: yes
• Core: 8051
• Processor Series: C8051
• Data Bus Width: 8 bit

16.2.6. 16-Bit Pulse Width Modulator Mode
A PCA module may also be operated in 16-bit PWM mode. In this mode, the 16-bit capture/compare mod-
ule defines the number of PCA clocks for the low time of the PWM signal. When the PCA counter matches
the module contents, the output on CEXn is set to ‘1’; when the counter overflows, CEXn is set to ‘0’. To
output a varying duty cycle, new value writes should be synchronized with PCA 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, match interrupts should be enabled (ECCFn = 1 AND MATn = 1) to help synchro-
nize the capture/compare register writes. The duty cycle for 16-bit PWM Mode is given by Equation 16.3.
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’.
Using Equation 16.3, the largest duty cycle is 100% (PCA0CPn = 0), and the smallest duty cycle is
0.0015% (PCA0CPn = 0xFFFF). A 0% duty cycle may be generated by clearing the ECOMn bit to ‘0’.
PCA0CPLn
Write to
Reset
PCA0CPHn
Write to
0
ENB
ENB
1
W
P
M
1
6
n
1
E
C
O
M
n
PCA0CPMn
C
A
P
P
n
0 0 x 0
C
A
P
N
n
M
A
T
n
PCA Timebase
O
G
T
n
Equation 16.3. 16-Bit PWM Duty Cycle
W
P
M
n
E
C
C
F
n
x
Figure 16.9. PCA 16-Bit PWM Mode
DutyCycle
Enable
PCA0CPHn
PCA0H
=
16-bit Comparator
Rev. 2.9

---------------------------------------------------- -
65536 PCA0CPn
PCA0CPLn
PCA0L
–
65536
Overflow
C8051F300/1/2/3/4/5
match
S
R

SET
CLR
Q
Q
CEXn
Crossbar
Port I/O
163