C8051F020 Silicon Laboratories Inc, C8051F020 Datasheet - Page 257
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C8051F020
Manufacturer Part Number
C8051F020
Description
IC 8051 MCU 64K FLASH 100TQFP
Manufacturer
Silicon Laboratories Inc
Series
C8051F02xr
Specifications of C8051F020
Core Processor
8051
Core Size
8-Bit
Speed
25MHz
Connectivity
EBI/EMI, SMBus (2-Wire/I²C), SPI, UART/USART
Peripherals
Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
Number Of I /o
64
Program Memory Size
64KB (64K x 8)
Program Memory Type
FLASH
Ram Size
4.25K x 8
Voltage - Supply (vcc/vdd)
2.7 V ~ 3.6 V
Data Converters
A/D 8x8b, 8x12b; D/A 2x12b
Oscillator Type
Internal
Operating Temperature
-40°C ~ 85°C
Package / Case
100-TQFP, 100-VQFP
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant
Eeprom Size
-
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23.2.5. 8-Bit Pulse Width Modulator Mode
Each module can be used independently to generate pulse width modulated (PWM) outputs on its associated CEXn
pin. The frequency of the output is dependent on the timebase for the PCA0 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 PCA0 counter/timer (PCA0L) is equal to the value in PCA0CPLn, the output on the CEXn pin will be
asserted high. When the count value in PCA0L overflows, the CEXn output will be asserted low (see Figure 23.8).
Also, when the counter/timer low byte (PCA0L) overflows from 0xFF to 0x00, PCA0CPLn is reloaded automatically
with the value stored in the counter/timer's high byte (PCA0H) 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 23.2.
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 23.2, 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’.
PCA0CPLn
Write to
Reset
PCA0CPHn
Write to
0
1
ENB
ENB
W
M
P
0
1
6
n
Figure 23.8. PCA 8-Bit PWM Mode Diagram
E
C
O
M
n
PCA0CPMn
C
A
P
P
n
0 0 x 0
C
A
P
N
n
Equation 23.2. 8-Bit PWM Duty Cycle
M
A
T
n
O
G
DutyCycle
T
n
W
P
M
n
E
C
C
F
n
x
PCA Timebase
Enable
=
PCA0CPHn
Comparator
PCA0CPLn
-------------------------------------------------- -
PCA0L
256 PCA0CPHn
8-bit
Rev. 1.4
–
Overflow
256
match
S
R
SET
CLR
Q
Q
C8051F020/1/2/3
CEXn
Crossbar
Port I/O
257