C8051F313R Silicon Labs, C8051F313R Datasheet - Page 210

• Manufacturer Part Number: C8051F313R
• Description: 8-bit Microcontrollers - MCU 8KB 10ADC
• Manufacturer: Silicon Labs

Specifications of C8051F313R

• Product Category: 8-bit Microcontrollers - MCU
• Core: 8051
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 25 MHz
• Program Memory Size: 8 KB
• Data Ram Size: 1.25 KB
• On-chip Adc: Yes
• Operating Supply Voltage: 2.7 V to 3.6 V
• Package / Case: QFN-28
• Mounting Style: SMD/SMT
• A/d Bit Size: 10 bit
• A/d Channels Available: 17
• Data Rom Size: 128 B
• Interface Type: I2C, SMBus, SPI, UART
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Number Of Programmable I/os: 25
• Number Of Timers: 5
• On-chip Dac: No
• Processor Series: C8051
• Program Memory Type: Flash
• Factory Pack Quantity: 1500
• Supply Voltage - Max: 3.6 V
• Supply Voltage - Min: 2.7 V

C8051F310/1/2/3/4/5/6/7
18.2.5. 8-Bit Pulse Width Modulator Mode
Each module can be used independently to generate a pulse width modulated (PWM) output on its associ-
ated CEXn pin. The frequency of the output is dependent on the timebase for the PCA counter/timer. The
duty cycle of the PWM output signal is varied using the module's PCA0CPLn capture/compare register.
When the value in the low byte of the PCA counter/timer (PCA0L) is equal to the value in PCA0CPLn, the
output on the CEXn pin will be set. When the count value in PCA0L overflows, the CEXn output will be
reset (see Figure 18.8). Also, when the counter/timer low byte (PCA0L) overflows from 0xFF to 0x00,
PCA0CPLn is reloaded automatically with the value stored in the module’s capture/compare high byte
(PCA0CPHn) without software intervention. Setting the ECOMn and PWMn bits in the PCA0CPMn register
enables 8-Bit Pulse Width Modulator mode. The duty cycle for 8-Bit PWM Mode is given by Equation 18.2.
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 18.2, the largest duty cycle is 100% (PCA0CPHn = 0), and the smallest duty cycle is
0.39% (PCA0CPHn = 0xFF). A 0% duty cycle may be generated by clearing the ECOMn bit to ‘0’.
210
PCA0CPLn
Write to
Reset
PCA0CPHn
Write to
0
ENB
ENB
1
W
P
M
1
6
n
0
Figure 18.8. PCA 8-Bit PWM Mode Diagram
O
M
E
C
n
PCA0CPMn
C
A
P
P
n
0 0 x 0
C
A
P
N
n
Equation 18.2. 8-Bit PWM Duty Cycle
M
A
T
n
O
G
T
n
W
DutyCycle
M
P
n
E
C
C
F
n
x
PCA Timebase
Enable
=
PCA0CPHn
Comparator
PCA0CPLn
Rev. 1.7
PCA0L

-------------------------------------------------- -
8-bit
256 PCA0CPHn
–
Overflow
256
match
S
R
SET
CLR

Q
Q
CEXn
Crossbar
Port I/O