AT32UC3B0512-A2UES ATMEL [ATMEL Corporation], AT32UC3B0512-A2UES Datasheet - Page 79

• Manufacturer Part Number: AT32UC3B0512-A2UES
• Description: 32-bit AVR Microcontroller
• Manufacturer: ATMEL [ATMEL Corporation]

12.2.2.3
12.2.2.4
12.2.2.5
Power Manager
ADC
Processor and Architecture
1. If the BOD level is higher than VDDCORE, the part is constantly resetted
1. Sleep Mode activation needs addtionnal A to D conversion
1. LDM instruction with PC in the register list and without ++ increments Rp
2. RETE instruction does not clear SREG[L] from interrupts
3. Exceptions when system stack is protected by MPU
4. Set the polarity CPOL to the required one.
5. Read the RXHOLDING register.
Transfers can now befin and RXREADY will now behave as expected.
If the BOD level is set to a value higher than VDDCORE and enabled by fuses, the part will
be in constant reset.
Fix/Workaround
Apply an external voltage on VDDCORE that is higher than the BOD level and is lower than
VDDCORE max and disable the BOD.
If the ADC sleep mode is activated when the ADC is idle the ADC will not enter sleep mode
before after the next AD conversion.
Fix/Workaround
Activate the sleep mode in the mode register and then perform an AD conversion.
For LDM with PC in the register list: the instruction behaves as if the ++ field is always set, ie
the pointer is always updated. This happens even if the ++ field is cleared. Specifically, the
increment of the pointer is done in parallel with the testing of R12.
Fix/Workaround
None.
The RETE instruction clears SREG[L] as expected from exceptions.
Fix/Workaround
When using the STCOND instruction, clear SREG[L] in the stacked value of SR before
returning from interrupts with RETE.
RETS behaves incorrectly when MPU is enabled and MPU is configured so thatsystem
stack is not readable in unprivileged mode.
Fix/Workaround
Workaround 1: Make system stack readable in unprivileged mode,
or
Workaround 2: Return from supervisor mode using rete instead of rets. This requires: 1.
Changing the mode bits from 001b to 110b before issuing the instruction.
Updating the mode bits to the desired value must be done using a single mtsr instruction so
it is done atomically. Even if this step is described in general as not safe in the UC technical
reference guide, it is safe in this very specific case.
2. Execute the RETE instruction.