ATTINY261A-MU Atmel, ATTINY261A-MU Datasheet - Page 101

• Manufacturer Part Number: ATTINY261A-MU
• Description: NO NEW DESIGNS, USE TINY261A-XU - 20MHZ, QFN/MLF,IND TEMP, G
• Manufacturer: Atmel

8197B–AVR–01/10
Figure 12-13. Phase and Frequency Correct PWM Mode, Timing Diagram
The Timer/Counter Overflow Flag (TOV1) is set each time the counter reaches BOTTOM. The
Interrupt Flag can be used to generate an interrupt each time the counter reaches the BOTTOM
value.
In the Phase and Frequency Correct PWM mode, the compare unit allows generation of PWM
waveforms on the OC1x pins. Setting the COM1x1:0 bits to two will produce a non-inverted
PWM and setting the COM1x1:0 to three will produce an inverted PWM output. Setting the
COM1A1:0 bits to one will enable complementary Compare Output mode and produce both the
non-inverted (OC1x) and inverted output (OC1x). The actual values will only be visible on the
port pin if the data direction for the port pin is set as output. The PWM waveform is generated by
clearing (or setting) the Waveform Output (OCW1x) at the Compare Match between OCR1x and
TCNT1 when the counter increments, and setting (or clearing) the Waveform Output at Compare
Match when the counter decrements. The PWM frequency for the output when using the Phase
and Frequency Correct PWM can be calculated by the following equation:
The N variable represents the number of steps in dual-slope operation. The value of N equals to
the TOP value.
The extreme values for the OCR1C Register represent special cases when generating a PWM
waveform output in the Phase and Frequency Correct PWM mode. If the OCR1C is set equal to
BOTTOM, the output will be continuously low and if set equal to MAX the output will be continu-
ously high for non-inverted PWM mode. For inverted PWM the output will have the opposite
logic values.
The general I/O port function is overridden by the Output Compare value (OC1x / OC1x) from
the Dead Time Generator, if either of the COM1x1:0 bits are set and the Data Direction Register
bits for the OC1X and OC1X pins are set as an output. If the COM1x1:0 bits are cleared, the
TCNTn
OCWnx
(COMnx = 2)
OCWnx
Period
(COMnx = 3)
1
f
OCnxPCPWM
2
=
f
------------ -
clkT1
N
3
OCnx Interrupt Flag Set
OCRnx Update
TOVn Interrupt Flag Set
101