ATA6603-EK Atmel, ATA6603-EK Datasheet - Page 118

• Manufacturer Part Number: ATA6603-EK
• Description: MCU, MPU & DSP Development Tools Demoboard LIN-MCM
• Manufacturer: Atmel

Specifications of ATA6603-EK

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

4.12.6.3
118
ATA6602/ATA6603
Fast PWM Mode
The fast Pulse Width Modulation or fast PWM mode (WGM02:0 = 3 or 7) provides a high fre-
quency PWM waveform generation option. The fast PWM differs from the other PWM option by
its single-slope operation. The counter counts from BOTTOM to TOP then restarts from BOT-
TOM. TOP is defined as 0xFF when WGM2:0 = 3, and OCR0A when WGM2:0 = 7. In
non-inverting Compare Output mode, the Output Compare (OC0x) is cleared on the compare
match between TCNT0 and OCR0x, and set at BOTTOM. In inverting Compare Output mode,
the output is set on compare match and cleared at BOTTOM. Due to the single-slope operation,
the operating frequency of the fast PWM mode can be twice as high as the phase correct PWM
mode that use dual-slope operation. This high frequency makes the fast PWM mode well suited
for power regulation, rectification, and DAC applications. High frequency allows physically small
sized external components (coils, capacitors), and therefore reduces total system cost.
In fast PWM mode, the counter is incremented until the counter value matches the TOP value.
The counter is then cleared at the following timer clock cycle. The timing diagram for the fast
PWM mode is shown in
togram for illustrating the single-slope operation. The diagram includes non-inverted and
inverted PWM outputs. The small horizontal line marks on the TCNT0 slopes represent compare
matches between OCR0x and TCNT0.
Figure 4-32. Fast PWM Mode, Timing Diagram
The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches TOP. If the inter-
rupt is enabled, the interrupt handler routine can be used for updating the compare value.
In fast PWM mode, the compare unit allows generation of PWM waveforms on the OC0x pins.
Setting the COM0x1:0 bits to two will produce a non-inverted PWM and an inverted PWM output
can be generated by setting the COM0x1:0 to three: Setting the COM0A1:0 bits to one allows
the OC0A pin to toggle on Compare Matches if the WGM02 bit is set. This option is not available
for the OC0B pin (see
the port pin if the data direction for the port pin is set as output. The PWM waveform is gener-
ated by setting (or clearing) the OC0x Register at the compare match between OCR0x and
TCNT0, and clearing (or setting) the OC0x Register at the timer clock cycle the counter is
cleared (changes from TOP to BOTTOM).
Period
TCNTn
OCn
OCn
1
Table 4-48 on page
2
Figure
3
4-32. The TCNT0 value is in the timing diagram shown as a his-
4
124). The actual OC0x value will only be visible on
5
6
7
(COMnx1:0 = 2)
(COMnx1:0 = 3)
TOVn Interrupt Flag Set
OCRnx Interrupt
OCRnx Update and
Flag Set
4921E–AUTO–09/09