PIC18F1230 MICROCHIP [Microchip Technology], PIC18F1230 Datasheet - Page 129

• Manufacturer Part Number: PIC18F1230
• Description: 18/20/28-Pin, Enhanced Flash Microcontrollers with nanoWatt Technology, High-Performance PWM and A/D
• Manufacturer: MICROCHIP [Microchip Technology]

FIGURE 13-14:
13.6.4
Center-aligned PWM signals are produced by the
module when the PWM time base is configured in a
Continuous Up/Down Count mode (see Figure 13-15).
The PWM compare output is driven to the active state
when the value of the Duty Cycle register matches the
value of PTMR and the PWM time base is counting
downwards (PTDIR = 1). The PWM compare output
will be driven to the inactive state when the PWM time
base is counting upwards (PTDIR = 0) and the value in
the PTMR register matches the duty cycle value. If the
value in a particular Duty Cycle register is zero, then
the output on the corresponding PWM pin will be
FIGURE 13-15:
© 2006 Microchip Technology Inc.
Start of
First
PWM
Period
PTPER
Cycle
Duty
0
CENTER-ALIGNED PWM
PWM Output
PTMR Value
DUTY CYCLE UPDATE TIMES IN CONTINUOUS UP/DOWN COUNT MODE WITH
DOUBLE UPDATES
START OF CENTER-ALIGNED PWM
PTMR
Value
Duty Cycle
Period/2
Advance Information
Duty Cycle Value Loaded from Buffer Register
Period
inactive for the entire PWM period. In addition, the
output on the PWM pin will be active for the entire PWM
period if the value in the Duty Cycle register is equal to
or greater than the value in the PTPER register.
Note:
New Values Written to Duty Cycle Buffer
PIC18F1230/1330
When the PWM is started in Center-
Aligned mode, the PWM Time Base
Period register (PTPER) is loaded into the
PWM Time Base register (PTMR) and the
PTMR is configured automatically to start
down counting. This is done to ensure that
all the PWM signals don’t start at the same
time.
Period
DS39758B-page 127