PIC16F73-I/SO Microchip Technology Inc., PIC16F73-I/SO Datasheet - Page 59

• Manufacturer Part Number: PIC16F73-I/SO
• Description: 28 PIN, 7 KB FLASH, 192 RAM, 22 I/O
• Manufacturer: Microchip Technology Inc.

Specifications of PIC16F73-I/SO

• A/d Inputs: 5-Channel, 8-Bit
• Cpu Speed: 5 MIPS
• Eeprom Memory: 0 Bytes
• Input Output: 22
• Interface: I2C/SPI/USART
• Memory Type: Flash
• Number Of Bits: 8
• Package Type: 28-pin SOIC
• Programmable Memory: 7K Bytes
• Ram Size: 192 Bytes
• Speed: 20 MHz
• Timers: 2-8-bit, 1-16-bit
• Voltage, Range: 2-5.5 V
• Lead Free Status / Rohs Status: RoHS Compliant part Electrostatic Device

8.5
In Pulse Width Modulation mode, the CCPx pin pro-
duces up to a 10-bit resolution PWM output. Since the
CCP1 pin is multiplexed with the PORTC data latch, the
TRISC<2> bit must be cleared to make the CCP1 pin
an output.
Figure 8-3 shows a simplified block diagram of the
CCP module in PWM mode.
For a step-by-step procedure on how to set up the CCP
module for PWM operation, see Section 8.5.3.
FIGURE 8-3:
A PWM output (Figure 8-4) has a time-base (period)
and a time that the output stays high (duty cycle). The
frequency of the PWM is the inverse of the period
(1/period).
FIGURE 8-4:
 2002 Microchip Technology Inc.
(Note 1)
Note:
CCPR1H (Slave)
Note 1: The 8-bit timer is concatenated with the 2-bit inter-
Duty Cycle Registers
Comparator
CCPR1L
RESET
TMR2
TMR2
TMR2 = PR2
PR2
Comparator
PWM Mode (PWM)
Duty Cycle
Clearing the CCP1CON register will force
the CCP1 PWM output latch to the default
low level. This is not the PORTC I/O data
latch.
nal Q clock or the 2 bits of the prescaler to create the
10-bit time-base.
Period
(1)
Clear Timer,
CCP1 pin and
latch D.C.
TMR2 = Duty Cycle
SIMPLIFIED PWM BLOCK
DIAGRAM
PWM OUTPUT
CCP1CON<5:4>
RESET
TMR2
TMR2 = PR2
R
S
Q
TRISC<2>
RC2/CCP1
8.5.1
The PWM period is specified by writing to the PR2
register. The PWM period can be calculated using the
following formula:
PWM frequency is defined as 1 / [PWM period].
When TMR2 is equal to PR2, the following three events
occur on the next increment cycle:
• TMR2 is cleared
• The CCP1 pin is set (exception: if PWM duty
• The PWM duty cycle is latched from CCPR1L into
8.5.2
The PWM duty cycle is specified by writing to the
CCPR1L register and to the CCP1CON<5:4> bits. Up
to 10-bit resolution is available. The CCPR1L contains
the eight MSbs and the CCP1CON<5:4> contains the
two LSbs. This 10-bit value is represented by
CCPR1L:CCP1CON<5:4>. The following equation is
used to calculate the PWM duty cycle in time:
CCPR1L and CCP1CON<5:4> can be written to at any
time, but the duty cycle value is not latched into
CCPR1H until after a match between PR2 and TMR2
occurs (i.e., the period is complete). In PWM mode,
CCPR1H is a read only register.
The CCPR1H register and a 2-bit internal latch are
used to double buffer the PWM duty cycle. This double
buffering is essential for glitchless PWM operation.
When the CCPR1H and 2-bit latch match TMR2, con-
catenated with an internal 2-bit Q clock or 2 bits of the
TMR2 prescaler, the CCP1 pin is cleared.
The maximum PWM resolution (bits) for a given PWM
frequency is given by the formula:
cycle = 0%, the CCP1 pin will not be set)
CCPR1H
Note:
Note:
PWM period =
PWM duty cycle = (CCPR1L:CCP1CON<5:4>) •
Resolution
The Timer2 postscaler (see Section 8.3) is
not used in the determination of the PWM
frequency. The postscaler could be used to
have a servo update rate at a different fre-
quency than the PWM output.
If the PWM duty cycle value is longer than
the PWM period, the CCP1 pin will not be
cleared.
PWM PERIOD
PWM DUTY CYCLE
(TMR2 prescale value)
[(PR2) + 1] • 4 • T
=
T
OSC
log
• (TMR2 prescale value)
(
PIC16F7X
log(2)
F
F
PWM
OSC
)
OSC
DS30325B-page 57
bits
•