AT90USB646 datasheet(110/456 Pages) ATMEL

110 / 456 page

110

7593L–AVR–09/12

AT90USB64/128

• Bits 5:4 – COM0B1:0: Compare Match Output B mode

These bits control the Output Compare pin (OC0B) behavior. If one or both of the COM0B1:0

bits are set, the OC0B output overrides the normal port functionality of the I/O pin it is connected

to. However, note that the Data Direction Register (DDR) bit corresponding to the OC0B pin

must be set in order to enable the output driver.

When OC0B is connected to the pin, the function of the COM0B1:0 bits depends on the

WGM02:0 bit setting. Table 14-1 shows the COM0A1:0 bit functionality when the WGM02:0 bits

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

Table 14-2 shows the COM0B1:0 bit functionality when the WGM02:0 bits are set to fast PWM

mode.

Note:

1. A special case occurs when OCR0B equals TOP and COM0B1 is set. In this case, the Com-

pare Match is ignored, but the set or clear is done at TOP. See “Fast PWM mode” on page 104

for more details.

Table 14-3 shows the COM0B1:0 bit functionality when the WGM02:0 bits are set to phase cor-

rect PWM mode.

Note:

1. A special case occurs when OCR0B equals TOP and COM0B1 is set. In this case, the Com-

pare Match is ignored, but the set or clear is done at TOP. See “Phase correct PWM mode” on

page 106 for more details.

• Bits 3, 2 – Res: Reserved bits

These bits are reserved bits in the Atmel AT90USB64/128 and will always read as zero.

Table 14-4.

Compare Output mode, non-PWM mode.

COM01

COM00

Description

Normal port operation, OC0B disconnected.

Toggle OC0B on Compare Match

Clear OC0B on Compare Match

Set OC0B on Compare Match

Table 14-5.

Compare Output mode, fast PWM mode

(1).

COM01

COM00

Description

Normal port operation, OC0B disconnected.

Reserved.

Clear OC0B on Compare Match, set OC0B at TOP.

Set OC0B on Compare Match, clear OC0B at TOP.

Table 14-6.

Compare Output mode, phase correct PWM mode (1).

COM0A1

COM0A0

Description

Normal port operation, OC0B disconnected.

Reserved.

Clear OC0B on Compare Match when up-counting. Set OC0B on Compare

Match when down-counting.

Set OC0B on Compare Match when up-counting. Clear OC0B on Compare

Match when down-counting.

AT90USB646 Datasheet(PDF) 110 Page - ATMEL Corporation

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