Datasheet

96
8197C–AVR–05/11
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 DTPS1[1:0] 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 t
non-overlap / rising edge
is adjusted by the 4-bit DT1H value and the
t
non-overlap / falling edge
is adjusted by the 4-bit DT1L value.
Figure 12-9. The Complementary Output Pair, COM1x[1:0] = 1
12.7 Compare Match Output Unit
The Compare Output Mode (COM1x[1:0]) bits have two functions. The Waveform Generator
uses the COM1x[1:0] bits for defining the inverted or non-inverted Waveform Output (OCW1x) at
the next Compare Match. Also, the COM1x[1:0] bits control the OC1x and OC1x
pin output
source. Figure 12-10 on page 97 shows a simplified schematic of the logic affected by the
COM1x[1:0] 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 COM1x[1:0] 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 COM1x[1:0] 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 COM1x[1:0] 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