Rainbow-electronics ATmega8515L Manual de usuario descargar pdf (Pagina 117)

117

ATmega8515(L)

2512A–AVR–04/02

Note: 1. A specialcaseoccurs when OCR1A/OCR1B equals TOPandCOM1A1/COM1B1is

set. See “Phase CorrectPWM Mode” on page 110. for more details.

• Bit 3 – FOC1A: Force Output Compare for Channel A

• Bit 2 – FOC1B: Force Output Compare for Channel B

The FOC1A/FOC1Bbits areonly active when the WGM13:0 bitsspecifies a non-PWM

mode. However, for ensuring compatibilitywithfuture devices, these bits must be set to

zero when TCCR1A iswritten when operating in a PWM mode. When writing a logical

onetothe FOC1A/FOC1Bbit, an immediate comparematch isforced on the waveform

generation unit. The OC1A/OC1B output ischanged according to itsCOM1x1:0 bitsset-

ting. Note that the FOC1A/FOC1Bbits areimplemented asstrobes.Thereforeitis the

value present in the COM1x1:0 bits that determine theeffectof the forcedcompare.

A FOC1A/FOC1Bstrobe will not generate any interruptnorwill it clear thetimer in Clear

Timer on Compare Match (CTC) modeusing OCR1A as TOP.

The FOC1A/FOC1Bbits arealways read aszero.

• Bit 1:0 – WGM11:0: Waveform Generation Mode

Combinedwith the WGM13:2 bitsfound in theTCCR1B Register, these bitscontrol the

counting sequenceof the counter, the source for maximum (TOP)counter value, and

what typeofwaveform generation to beused, see Table53. Modes of operation sup-

portedbytheTimer/Counter unit are:Normal mode (counter), Clear Timer on Compare

match (CTC) mode, and three types of Pulse WidthModulation (PWM) modes. See

“Modes ofOperation” on page 106.

Table 52. Compare Output Mode, Phase Correctand PhaseandFrequency Correct

PWM

(1)

COM1A1/

COM1B1

COM1A0/

COM1B0 Description

00Normalportoperation,OC1A/OC1Bdisconnected.

01WGM13=0:Normalportoperation,OC1A/OC1Bdisconnected.

WGM13=1: Togg le OC1A on comparematch, OC1Breserved.

10ClearOC1A/OC1B on comparematch when up-counting. Set

OC1A/OC1B on comparematch when downcounting.

11Set OC1A/OC1B on comparematch when up-counting. Clear

OC1A/OC1B on comparematch when downcounting.

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