Rainbow-electronics ATmega64L Bedienungsanleitung PDF herunterladen (Seite 78)

ATmega16(L)

2466B–09/01

Note: 1. The CTC0 and PWM0 bit definition names are now obsolete. Use the WGM01:0 def-

initions. However, the functionality and location of these bits are compatible with

previous versions of the timer.

• Bit 5:4 - COM01:0: Compare Match Output Mode

These bits control the output compare pin (OC0) behavior. If one or both of the

COM01:0 bits are set, the OC0 output overrides the normal port functionality of the I/O

pin it is connected to. However, note that the Data Direction Register (DDR) bit corre-

sponding to the OC0 pin must be set in order to enable the output driver.

When OC0 is connected to the pin, the function of the COM01:0 bits depends on the

WGM01:0 bit setting. Table 39 shows the COM01:0 bit functionality when the WGM01:0

bits are set to a normal or CTC mode (non-PWM).

Table 40 shows the COM01:0 bit functionality when the WGM01:0 bits are set to fast

PWM mode.

Note: 1. A special case occurs when OCR0 equals TOP and COM01 is set. In this case, the

compare match is ignored, but the set or clear is done at TOP. See “Fast PWM Mode”

on page 73 for more details.

Table 41 shows the COM01:0 bit functionality when the WGM01:0 bits are set to phase

correct PWM mode.

Table 38. Waveform Generation Mode Bit Description

(1)

Mode

WGM01

(CTC0)

WGM00

(PWM0)

Timer/Counter Mode

of Operation TOP

Update of

OCR0

TOV0 Flag

Set-on

0 0 0 Normal 0xFF Immediate MAX

1 0 1 PWM, Phase Correct 0xFF TOP BOTTOM

2 1 0 CTC OCR0 Immediate MAX

31 1Fast PWM 0xFFTOPMAX

Table 39. Compare Output Mode, non-PWM Mode

COM01 COM00 Description

0 0 Normal port operation, OC0 disconnected.

01Toggle

OC0 on compare match

1 0 Clear

OC0 on compare match

11Set OC0 on compare match

Table 40. Compare Output Mode, Fast PWM Mode

(1)

COM01 COM00 Description

0 0 Normal port operation,

OC0 disconnected.

01Reserved

10Clear

OC0 on compare match, set OC0 at TOP

11Set

OC0 on compare match, clear OC0 at TOP

1 2 ... 73 74 75 76 77 78 79 80 81 82 83 ... 297 298

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