AT89LP828 Atmel Corporation, AT89LP828 Datasheet - Page 50

• Manufacturer Part Number: AT89LP828
• Manufacturer: Atmel Corporation

Specifications of AT89LP828

• Flash (kbytes): 8 Kbytes
• Max. Operating Frequency: 25 MHz
• Cpu: 8051-1C
• Max I/o Pins: 30
• Spi: 1
• Uart: 1
• Sram (kbytes): 0.75
• Eeprom (bytes): 1024
• Self Program Memory: IAP
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 3
• Isp: SPI/OCD
• Watchdog: Yes

11.5.4
50
AT89LP428/828
Mode 3 – Split 8-bit PWM
Figure 11-9. PWM Mode 2 Waveform
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 AT89LP428/828 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.
Mode 3:
Mode 3, T1:
THx
Mode 3, T0:
FFh
Tx
f
OUT
Duty Cycle %
Duty Cycle %
=
Oscillator Frequency
------------------------------------------------------ -
256
=
=
100
100
×
×
RH0
----------- -
RL0
---------- -
256
256
×
-------------------- -
TPS
1
+
Figure
1
11-10. Only the Timer
3654A–MICRO–8/09