AT32UC3L064_11 ATMEL [ATMEL Corporation], AT32UC3L064_11 Datasheet - Page 98

• Manufacturer Part Number: AT32UC3L064_11
• Description: 32-bit Atmel AVR Microcontroller
• Manufacturer: ATMEL [ATMEL Corporation]

10.4.14
32099HS–12/2011
TWI
3. SPI disable does not work in SLAVE mode
4. SPI bad serial clock generation on 2nd chip_select when SCBR=1, CPOL=1, and
5. SPI mode fault detection enable causes incorrect behavior
1. TWI pins are not SMBus compliant
2. PA21, PB04, and PB05 are not 5V tolerant
3. PB04 SMBALERT function should not be used
4. TWIM STOP bit in IMR always reads as zero
5. Disabled TWIM drives TWD and TWCK low
Disable the PDCA, add two NOPs, and disable the SPI. To continue the transfer, enable the
SPI and PDCA.
SPI disable does not work in SLAVE mode.
Fix/Workaround
Read the last received data, then perform a software reset by writing a one to the Software
Reset bit in the Control Register (CR.SWRST).
NCPHA=0
When multiple chip selects (CS) are in use, if one of the baudrates equal 1 while one
(CSRn.SCBR=1) of the others do not equal 1, and CSRn.CPOL=1 and CSRn.NCPHA=0,
then an additional pulse will be generated on SCK.
Fix/Workaround
When multiple CS are in use, if one of the baudrates equals 1, the others must also equal 1
if CSRn.CPOL=1 and CSRn.NCPHA=0.
When mode fault detection is enabled (MR.MODFDIS==0), the SPI module may not operate
properly.
Fix/Workaround
Always disable mode fault detection before using the SPI by writing a one to MR.MODFDIS.
The TWI pins draw current when they are supplied with 3.3V and the part is left unpowered.
Fix/Workaround
None.
Pins PA21, PB04, and PB05 are only 3.3V tolerant.
Fix/Workaround
None.
The SMBALERT function from TWIMS0 should not be selected on pin PB04.
Fix/Workaround
None.
The STOP bit in IMR always reads as zero.
Fix/Workaround
None.
When the TWIM is disabled, it drives the TWD and TWCK signals with logic level zero. This
can lead to communication problems with other devices on the TWI bus.
Fix/Workaround
Enable the TWIM first and then enable the TWD and TWCK peripheral pins in the GPIO
controller. If it is necessary to disable the TWIM, first disable the TWD and TWCK peripheral
pins in the GPIO controller and then disable the TWIM.
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