AT89LP428 Atmel Corporation, AT89LP428 Datasheet - Page 71

• Manufacturer Part Number: AT89LP428
• Manufacturer: Atmel Corporation

Specifications of AT89LP428

• Flash (kbytes): 4 Kbytes
• Max. Operating Frequency: 25 MHz
• Cpu: 8051-1C
• Max I/o Pins: 30
• Spi: 1
• Uart: 1
• Sram (kbytes): 0.75
• Eeprom (bytes): 512
• Self Program Memory: IAP
• Operating Voltage (vcc): 2.4 to 5.5
• Timers: 3
• Isp: SPI/OCD
• Watchdog: Yes

13.4.2.1
13.4.2.2
3654A–MICRO–8/09
Phase and Frequency Correct PWM
Phase Correct PWM
Figure 13-9. Non-overlapping Waveforms Using Symmetrical PWM
When T2CM
this mode the compare value double buffer is only updated when the timer equals MIN (under-
flow). This guarantees that the resulting waveform is always symmetrical around the TOP value
as shown in
TF2 interrupt flag is only set at underflow.
When T2CM
compare value double buffer is updated when the timer equals MIN (underflow) and TOP (over-
flow). The resulting waveform may not be completely symmetrical around the TOP value as
shown in
However, this allows the pulses to be weighted toward one edge or another. The TF2 interrupt
flag is set at both underflow and overflow.
Figure 13-10. Phase and Frequency Correct Symmetrical (Center-Aligned) PWM
(Non-Inverted) CCB
{RCAP2H,RCA2L}
{RCAP2H,RCA2L}
(Inverted) CCA
{CCAH,CCAL}
{CCBH,CCBL}
{CCxH,CCxL}
Non-Inverted
Figure 13-11
Inverted
1-0
1-0
CCx
Figure 13-10
= 10B, the Symmetrical PWM operates in phase and frequency correct mode. In
= 11B, the Symmetrical PWM operates in phase correct mode. In this mode the
because the up and down count compare values may not be identical.
because the up and down count compare values are identical. The
CP/RL2 = 0, T2CM
CP/RL2 = 0, T2CM
1-0
1-0
= 10B, DCEN = 0
= 10B, DCEN = 0
AT89LP428/828
Duty Cycle Updated
71