![](http://datasheet.mmic.net.cn/100000/IF180C52TXXX-20R_datasheet_3493957/IF180C52TXXX-20R_818.png)
818
32099I–01/2012
AT32UC3L016/32/64
The TWALM signal in the TWIM is active high instead of active low.
Fix/Workaround
Use an external inverter to invert the signal going into the TWIM. When using both TWIM
and TWIS on the same pins, the TWALM cannot be used.
3.
TWIS may not wake the device from sleep mode
If the CPU is put to a sleep mode (except Idle and Frozen) directly after a TWI Start condi-
tion, the CPU may not wake upon a TWIS address match. The request is NACKed.
Fix/Workaround
When using the TWI address match to wake the device from sleep, do not switch to sleep
modes deeper than Frozen. Another solution is to enable asynchronous EIC wake on the
TWIS clock (TWCK) or TWIS data (TWD) pins, in order to wake the system up on bus
events.
4.
SMBALERT bit may be set after reset
The SMBus Alert (SMBALERT) bit in the Status Register (SR) might be erroneously set after
system reset.
Fix/Workaround
After system reset, clear the SR.SMBALERT bit before commencing any TWI transfer.
5.
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.
6.
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.
35.2.10
PWMA
1.
BUSY bit is never cleared after writes to the Control Register (CR)
When writing a non-zero value to CR.TOP, CR.SPREAD, or CR.TCLR when the PWMA is
disabled (CR.EN == 0), the BUSY bit in the Status Register (SR.BUSY) will be set, but never
cleared.
Fix/Workaround
When writing a non-zero value to CR.TOP, CR.SPREAD, or CR.TCLR, make sure the
PWMA is enabled, or simultaneously enable the PWMA by writing a one to CR.EN.
2.
Incoming peripheral events are discarded during duty cycle register update
Incoming peripheral events to all applied channels will be discarded if a duty cycle update is
received from the user interface in the same PWMA clock period.
Fix/Workaround
Ensure that duty cycle writes from the user interface are not performed in a PWMA period
when an incoming peripheral event is expected.