C8051F321R Silicon Laboratories Inc, C8051F321R Datasheet - Page 242

• Manufacturer Part Number: C8051F321R
• Description: IC 8051 MCU 16K FLASH 28MLP
• Manufacturer: Silicon Laboratories Inc
• Series: C8051F32xr

Specifications of C8051F321R

• Core Processor: 8051
• Core Size: 8-Bit
• Speed: 25MHz
• Connectivity: SMBus (2-Wire/I²C), SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 21
• Program Memory Size: 16KB (16K x 8)
• Program Memory Type: FLASH
• Ram Size: 2.25K x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 3.6 V
• Data Converters: A/D 13x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 28-VQFN Exposed Pad, 28-HVQFN, 28-SQFN, 28-DHVQFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Eeprom Size: -
• Other names: 336-1067-2

C8051F320/1
20.2.5. 8-Bit Pulse Width Modulator Mode
Each module can be used independently to generate a pulse width modulated (PWM) output on its associated 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 20.8). Also, when the counter/timer low
byte (PCA0L) overflows from 0xFF to 0x00, PCA0CPLn is reloaded automatically with the value stored in the mod-
ule’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 20.2.
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’.
242
Equation 20.2. 8-Bit PWM Duty Cycle
DutyCycle
=
Rev. 1.1
(
-------------------------------------------------- -
256 PCA0CPHn
–
256
)