Rainbow-electronics ATmega8515L Manuel d'utilisateur télécharger pdf (Page 103)

103

ATmega8515(L)

2512A–AVR–04/02

measuring frequency only, the clearing of the ICF1 flag is not required(if an interrupt

handler is used).

Output Compare Units The16-bit comparatorcontinuously compares TCNT1 with the

Output Compare Regis-

ter

(OCR1x). If TCNTequals OCR1x the comparatorsignals amatch.Amatch will set

the

Output Compare Flag

(OCF1x) at thenexttimerclock cycle. If enabled(OCIE1x=

1), theoutput compare flag generates an output compareinterrupt. The OCF1xflag is

automatically clearedwhen theinterruptis executed.Alternatively the OCF1xflag can

be clearedbysoftware by writing a logical onetoitsI/Obit location. The waveform gen-

erator uses thematch signal to generateanoutput according to operating mode set by

the

Waveform Generation mode

(WGM13:0)bits and

Compare Output mode

(COM1x1:0)bits.TheTOPandBOTTOM signals areusedbythe waveform generator

forhandling the specialcases of theextreme values in some modes of operation. See

“Modes ofOperation” on page 106.

A specialfeatureof output compareunitAallows it to define theTimer/Counter TOP

value (i.e.,counterresolution). Inadditiontothe counterresolution, theTOPvalue

defines the period time forwaveforms generatedbythe waveform generator.

Figure49shows a block diagram of the output compareunit.The small “n” in the regis-

ter andbit names indicates the devicenumber(n = 1 for Timer/Counter1), and the“x”

indicates output compare unit (A/B).Theelements of the block diagram that are not

directly a partof the output compare unit aregrayshaded.

Figure 49. Output Compare Unit,Block Diagram

The OCR1xregister isdouble bufferedwhen using any of thetwelve

Pulse Width Modu-

lation

(PWM) modes. For thenormal and

Clear Timer on Compare

(CTC) modes of

operation, the double buffering isdisabled.The double buffering synchronizes the

update of the OCR1xCompare Register to either TOPorBOTTOM of the counting

OCFnx (Int.Req.)

(16-bit Comparator )

OCRnx Buffer (16-bit Register)

OCRnxH Buf. (8-bit)

OCnx

TEMP (8-bit)

DATA BUS

(8-bit)

OCRnxL Buf. (8-bit)

TCNTn (16-bit Counter)

TCNTnH (8-bit) TCNTnL (8-bit)

COMnx1:0WGMn3:0

OCRnx (16-bit Register)

OCRnxH (8-bit) OCRnxL (8-bit)

Waveform Generator

TOP

BOTTOM

1 2 ... 98 99 100 101 102 103 104 105 106 107 108 ... 222 223

Commentaires sur ces manuels

Pas de commentaire

Rainbow-electronics ATmega8515L Manuel d'utilisateur Page 103

Commentaires sur ces manuels

Produits connexes et manuels pour Capteurs Rainbow-electronics ATmega8515L