at89lp214-20xi ATMEL Corporation, at89lp214-20xi Datasheet - Page 35

• Manufacturer Part Number: at89lp214-20xi
• Description: At89lp213 8-bit Microcontroller With 2k Bytes Flash
• Manufacturer: ATMEL Corporation

14.5.4
3538B–MICRO–11/07
Mode 3 – Split 8-bit PWM
Timer 1 in PWM Mode 3 simply holds its count. The effect is the same as setting TR1 = 0.
Timer 0 in PWM Mode 3 establishes TL0 and TH0 as two separate PWM counters in a manner
similar to normal Mode 3. PWM Mode 3 on Timer 0 is shown in
Prescaler is available to change the output frequency during PWM Mode 3. TL0 can use the
Timer 0 control bits: GATE, TR0, INT0, PWM0EN and TF0. TH0 is locked into a timer function
and uses TR1, PWM1EN and TF1. RL0 provides the duty cycle for TL0 and RH0 provides the
duty cycle for TH0.
PWM Mode 3 is for applications requiring a single PWM channel and two timers, or two PWM
channels and an extra timer or counter. With Timer 0 in PWM Mode 3, the AT89LP213 can
appear to have three Timer/Counters. When Timer 0 is in PWM Mode 3, Timer 1 can be turned
on and off by switching it out of and into its own Mode 3. In this case, Timer 1 can still be used by
the serial port as a baud rate generator or in any application not requiring an interrupt. The fol-
lowing formulas give the output frequency and duty cycle for Timer 0 in PWM Mode 3.
Figure 14-9. Timer/Counter 0 PWM Mode 3
INT1 Pin
GATE
Mode 3:
Mode 3, T1:
Mode 3, T0:
TR1
OSC
OSC
TR1
f
out
÷TPS
÷TPS
Duty Cycle %
Duty Cycle %
=
Oscillator Frequency
------------------------------------------------------ -
Control
256
=
=
100
100
(8 Bits)
(8 Bits)
(8 Bits)
(8 Bits)
OCR0
OCR1
RL0
RH0
TL0
TH0
×
×
RH 0
----------- -
RL0
---------- -
256
256
×
=
=
------------------- -
TPS
1
+
AT89LP213/214
1
Figure
14-9. Only the Timer
T0
T1
35