ATTINY817-MFR. datasheet(149/492 Pages) MICROCHIP

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With Buffering: When double buffering is used, the buffer can be written at any time and still maintain

correct operation. The TCA.PER is always updated on the UPDATE condition, as shown for dual-slope

operation in the figure below. This prevents wraparound and the generation of odd waveforms.

Figure 20-8. Changing the Period Using Buffering

CNT

BOTTOM

MAX

"update"

"write"

New Period written to

PERB that is higher

than current CNT.

New Period written to

PERB that is lower

than current CNT.

New PER is updated

with PERB value.

20.3.3.4 Compare Channel

Each Compare Channel n continuously compares the counter value (TCA.CNT) with the Compare n

set the Compare Channel's interrupt flag at the next timer clock cycle, and the optional interrupt is

generated.

The Compare n Buffer register (TCA.CMPnBUF) provides double buffer capability equivalent to that for

the period buffer. The double buffering synchronizes the update of the TCA.CMPn register with the buffer

value to either the TOP or BOTTOM of the counting sequence, according to the UPDATE condition. The

synchronization prevents the occurrence of odd-length, non-symmetrical pulses for glitch-free output.

Waveform Generation

The compare channels can be used for waveform generation on the corresponding port pins. To make

the waveform visible on the connected port pin, the following requirements must be fulfilled:

A waveform generation mode must be selected by writing the WGMODE bit field in TCA.CTRLB.

The TCA is counting clock tick, not Events (CNTEI=0 in TCA.EVCTRL)

The compare channels used must be enabled (CMPnEN=1 in TCA.CTRLB). This will override the

corresponding PORT pin output register. An alternative pin can be selected by writing to the

respective TCA Waveform Output n bit (TCA0n) in the Control C register of the Port Multiplexer

(PORTMUX.CTRLC).

The direction for the associated Port pin n must be configured as output (PORT.DIR[n]=1).

Optional: Enable inverted waveform output for the associated Port pin n (INVEN=1 in PORT.PINn).

Frequency (FRQ) Waveform Generation

For frequency generation, the period time (T) is controlled by a TCA.CMPn register instead of the Period

the TCA.CNT and TCA.CMPn registers.

ATtiny417/817

Datasheet Complete

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