Datasheet
103
9166DS–AVR-01/12
AT32UC3C
10.2.10 TWIS
1 Clearing the NAK bit before the BTF bit is set locks up the TWI bus
When the TWIS is in transmit mode, clearing the NAK Received (NAK) bit of the Status Reg-
ister (SR) before the end of the Acknowledge/Not Acknowledge cycle will cause the TWIS to
attempt to continue transmitting data, thus locking up the bus.
Fix/Workaround
Clear SR.NAK only after the Byte Transfer Finished (BTF) bit of the same register has been
set.
2 TWIS stretch on Address match error
When the TWIS stretches TWCK due to a slave address match, it also holds TWD low for
the same duration if it is to be receiving data. When TWIS releases TWCK, it releases TWD
at the same time. This can cause a TWI timing violation.
Fix/Workaround
None.
3 TWALM forced to GND
The TWALM pin is forced to GND when the alternate function is selected and the TWIS
module is enabled.
Fix/Workaround
None.
10.2.11 USBC
1 UPINRQx.INRQ field is limited to 8-bits
In Host mode, when using the UPINRQx.INRQ feature together with the multi-packet mode
to launch a finite number of packet among multi-packet, the multi-packet size (located in the
descriptor table) is limited to the UPINRQx.INRQ value multiply by the pipe size.
Fix/Workaround
UPINRQx.INRQ value shall be less than the number of configured multi-packet.
2 In USB host mode, downstream resume feature does not work (UHCON.RESUME=1).
Fix/Workaround
None.
3 In host mode, the disconnection during OUT transition is not supported
In USB host mode, a pipe can not work if the previous USB device disconnection has
occurred during a USB transfer.
Fix/Workaround
Reset the USBC (USBCON.USB=0 and =1) after a device disconnection (UHINT.DDISCI).
4 In USB host mode, entering suspend mode can fail
In USB host mode, entering suspend mode can fail when UHCON.SOFE=0 is done just
after a SOF reception (UHINT.HSOFI).
Fix/Workaround
Check that UHNUM.FLENHIGH is below 185 in Full speed and below 21 in Low speed
before clearing UHCON.SOFE.
5 In USB host mode, entering suspend mode for low speed device can fail when the
USB freeze (USBCON.FRZCLK=1) is done just after UHCON.SOFE=0.
Fix/Workaround
When entering suspend mode (UHCON.SOFE is cleared), check that USBFSM.DRDSTATE
is not equal to three before freezing the clock (USBCON.FRZCLK=1).