PIC18F1230 MICROCHIP [Microchip Technology], PIC18F1230 Datasheet - Page 124

• 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]

PIC18F1230/1330
13.4.4
This mode is available in Continuous Up/Down Count
mode. In the Double Update mode (PTMOD<1:0> = 11),
an interrupt event is generated each time the PTMR
register is equal to zero and each time the PTMR
matches the PTPER register. Figure 13-8 shows the
interrupts in Continuous Up/Down Count mode with
double updates.
The Double Update mode provides two additional
functions to the user in Center-Aligned mode.
1.
FIGURE 13-8:
DS39758B-page 122
Note 1: Interrupt flag bit, PTIF, is sampled here (every Q1).
PTMR_INT_REQ
PTMR_INT_REQ
A: PRESCALER = 1:1
The control loop bandwidth is doubled because
the PWM duty cycles can be updated twice per
period.
PTDIR bit
PTDIR bit
2: PWM Time Base Period register, PTPER, is loaded with the value 3FFh for this example.
PTIF bit
PTIF bit
PTMR
PTMR
OSC1
OSC1
INTERRUPTS IN DOUBLE UPDATE
MODE
Case 1: PTMR Counting Upwards
Case 2: PTMR Counting Downwards
Q1
Q1
1
1
Q2
Q2
PWM TIME BASE INTERRUPTS, CONTINUOUS UP/DOWN COUNT MODE WITH
DOUBLE UPDATES
3FDh
002h
Q3
Q3
Q4
Q4
Q1
Q1
1
1
Q2
Q2
3FEh
001h
Advance Information
Q3
Q3
Q4
Q4
Q1
Q1
1
1
2
Q2
Q2
2.
000h
3FFh
Note:
Q3
Q3
Asymmetrical center-aligned PWM waveforms
can be generated, which are useful for
minimizing output waveform distortion in certain
motor control applications.
Q4
Q4
Do not change the PTMOD bits while
PTEN is active. It will yield unexpected
results. To change the PWM Timer mode
of operation, first clear the PTEN bit, load
PTMOD bits with required data and then
set PTEN.
Q1
Q1
1
1
Q2
Q2
3FEh
001h
Q3
Q3
© 2006 Microchip Technology Inc.
Q4
Q4
Q1
Q1
Q2
Q2
3FDh
002h
Q3
Q3
Q4
Q4