ATtiny261A datasheet(95/292 Pages) ATMEL

95 / 292 page

8197A–AVR–10/09

ATtiny261A/461A/861A

zero. The outputs OC1x and OC1x are inverted, if the PWM Inversion Mode bit PWM1X is set.

This will also cause both outputs to be high during the dead time.

The length of the counting period is user adjustable by selecting the dead time prescaler setting

by using the DTPS11:10 control bits, and selecting then the dead time value in I/O register DT1.

The DT1 register consists of two 4-bit fields, DT1H and DT1L that control the dead time periods

of the PWM output and its' complementary output separately in terms of the number of pres-

caled dead time generator clock cycles. Thus the rising edge of OC1x and OC1x can have

different dead time periods as the tnon-overlap / rising edge is adjusted by the 4-bit DT1H value and the

tnon-overlap / falling edge is adjusted by the 4-bit DT1L value.

Figure 12-9. The Complementary Output Pair, COM1x1:0 = 1

12.7 Compare Match Output Unit

The Compare Output Mode (COM1x1:0) bits have two functions. The Waveform Generator uses

the COM1x1:0 bits for defining the inverted or non-inverted Waveform Output (OCW1x) at the

next Compare Match. Also, the COM1x1:0 bits control the OC1x and OC1x pin output source.

Figure 12-10 on page 96 shows a simplified schematic of the logic affected by the COM1x1:0 bit

setting. The I/O Registers, I/O bits, and I/O pins in the figure are shown in bold. Only the parts of

the general I/O Port Control Registers (DDR and PORT) that are affected by the COM1x1:0 bits

are shown.

In Normal Mode (non-PWM) the Dead Time Generator is disabled and it is working like a syn-

chronizer: the Output Compare (OC1x) is delayed from the Waveform Output (OCW1x) by one

timer clock cycle. Whereas in Fast PWM Mode and in Phase and Frequency Correct PWM

Mode when the COM1x1:0 bits are set to “01” both the non-inverted and the inverted Output

Compare output are generated, and an user programmable Dead Time delay is inserted for

these complementary output pairs (OC1x and OC1x). The functionality in PWM modes is similar

to Normal mode when any other COM1x1:0 bit setup is used. When referring to the OC1x state,

the reference is for the Output Compare output (OC1x) from the Dead Time Generator, not the

OC1x pin. If a system reset occur, the OC1x is reset to “0”.

OCnx

(COMnx = 1)

t non-overlap / rising edge

t non-overlap / falling edge

OCnx

OCWnx

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