attiny167-esxz ATMEL Corporation, attiny167-esxz Datasheet - Page 90

• Manufacturer Part Number: attiny167-esxz
• Description: 8-bit Avr 8-bit Microcontroller Microcontroller With 16k Bytes In-system Programmable Flash And Lin Controller
• Manufacturer: ATMEL Corporation

10.7.3
90
ATtiny167
Fast PWM Mode
the pin is set to output. The waveform generated will have a maximum frequency of f
f
equation:
The N variable represents the prescale factor (1, 8, 32, 64, 128, 256, or 1024).
As for the Normal mode of operation, the TOV0 flag is set in the same timer clock cycle that the
counter counts from MAX to 0x00.
The fast Pulse Width Modulation or fast PWM mode (WGM01:0 = 3) provides a high frequency
PWM waveform generation option. The fast PWM differs from the other PWM option by its
single-slope operation. The counter counts from BOTTOM to MAX then restarts from BOTTOM.
In non-inverting Compare Output mode, the Output Compare (OC0A) is cleared on the compare
match between TCNT0 and OCR0A, 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 uses 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 MAX 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 OCR0A and TCNT0.
Figure 10-6. Fast PWM Mode, Timing Diagram
The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches MAX. If the inter-
rupt is enabled, the interrupt handler routine can be used for updating the compare value.
clk_I/O
TCNTn
OCnx
OCnx
Period
/2 when OCR0A is set to zero (0x00). The waveform frequency is defined by the following
1
Figure
2
10-6. The TCNT0 value is in the timing diagram shown as a his-
3
f
OCnx
4
=
------------------------------------------------- -
2 N
⋅
5
⋅
f
(
clk_I/O
1
+
OCRnx
6
)
7
OCRnx Interrupt Flag Set
OCRnx Update and
TOVn Interrupt Flag Set
(COMnx1:0 = 2)
(COMnx1:0 = 3)
7728A–AUTO–07/08
OC0A
=