AT32UC3L064_2 Datasheet, PDF (798/830 Pages) ATMEL Corporation – 32-bit AVR® Microcontroller

35.1.8 SPI
35.1.9 TWI
32099D–06/2010
AT32UC3L016/32/64
1. SPI disable does not work in SLAVE mode
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).
2. SPI Bad Serial Clock Generation on 2nd chip select when SCBR==1, CPOL==1, and
NCPHA==0
When multiple chip selects are in use, if one of the baudrates is equal to 1
(CSRn.SCBR==1) and one of the others is not equal to 1, and CSRn.CPOL==1 and
CSRn.NCPHA==0, an additional pulse will be generated on SCK.
Fix/Workaround
When multiple chip selects are in use, if one of the baudrates is equal to 1, the others must
also be equal to 1 if CSRn.CPOL==1 and CSRn.NCPHA==0.
3. SPI data transfer hangs with CSR0.CSAAT==1 and MR.MODFDIS==0
When CSR0.CSAAT==1 and mode fault detection is enabled (MR.MODFDIS==0), the SPI
module will not start a data transfer.
Fix/Workaround
Disable mode fault detection by writing a one to MR.MODFDIS.
4. Disabling SPI has no effect on the SR.TDRE bit
Disabling SPI has no effect on SR.TDRE whereas the write data command is filtered when
SPI is disabled. This means that as soon as the SPI is disabled it becomes impossible to
reset the SR.TDRE bit by writing to TDR. So if the SPI is disabled during a PDCA transfer,
the PDCA will continue to write data to TDR (as SR.TDRE stays high) until its buffer is
empty, and all data written after the disable command is lost.
Fix/Workaround
Disable the PDCA, add 2 NOP (minimum), and disable the SPI. To continue the transfer,
enable the SPI and the PDCA.
5. SPI mode fault detection enable causes incorrect behavior
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.
1. TWIM.SR.IDLE goes high immediately when NAK is received
When a NAK is received and there is a non-zero number of bytes to be transmitted,
SR.IDLE goes high immediately and does not wait for the STOP condition to be sent. This
does not cause any problem just by itself, but can cause a problem if software waits for
SR.IDLE to go high and then immediately disables the TWIM by writing a one to CR.MDIS.
Disabling the TWIM causes the TWCK and TWD pins to go high immediately, so the STOP
condition will not be transmitted correctly.
Fix/Workaround
If possible, do not disable the TWIM. If it is absolutely necessary to disable the TWIM, there
must be a software delay of at least two TWCK periods between the detection of
SR.IDLE==1 and the disabling of the TWIM.
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