AT90USB646 datasheet(424/435 Pages) ATMEL

424 / 435 page

424

7593D–AVR–07/06

AT90USB64/128

34. Errata

The revision letter in this section refers to the revision of the AT90USB64/128 device.

34.1

AT90USB1287/6 Rev B

• USB signal rate

• Spike on TWI pins when TWI is enabled

• High current consumption in sleep mode

• Async timer interrupt wake up from sleep generate multiple interrupts

UBS signal rate

The average USB signal rate may sometime be measured out of the USB specifications

(12MHz ±30kHz) with short frames. When measured on a long period, the average signal

rate value complies with the specifications. This bit rate deviation does not generates com-

munication or functional errors.

Problem fix/workaround

None.

Spike on TWI pins when TWI is enabled

100 ns negative spike occurs on SDA and SCL pins when TWI is enabled.

Problem Fix/workaround

No known workaround, enable AT90USB64/128 TWI first versus the others nodes of the

TWI network.

High current consumption in sleep mode

If a pending interrupt cannot wake the part up from the selected mode, the current consump-

tion will increase during sleep when executing the SLEEP instruction directly after a SEI

instruction.

Problem Fix/workaround

Before entering sleep, interrupts not used to wake up the part from the sleep mode should

be disabled.

Asynchronous timer interrupt wake up from sleep generates multiple interrupts

If the CPU core is in sleep and wakes-up from an asynchronous timer interrupt and then go

back in sleep mode again it may wake up several times.

Problem Fix/workaround

A software workaround is to wait with performing the sleep instruction until

TCNT2>OCR2+1.

AT90USB646 Datasheet(PDF) 424 Page - ATMEL Corporation