Errata
•
•
•
•
•
•
Brown-out Detector may cause the Device to be Stuck in Reset State
PWM not Phase Correct
Increased Interrupt Latency
Interrupt Return Fails when Stack Pointer Addresses the External Memory
Writing UBBRH Affects both UART0 and UART1
Store Program Memory Instruction May Fail
6. Brown-out Detecor may cause the Device to be Stuck in Reset State
When the internal Brown-out Detector is enabled, the device may hang in Reset
state regardless of the VCC level.
Problem Fix/Workaround
Use external Brown-out Detector and do not enable internal Brown-out Detector
(leave BODEN Fuse unprogrammed).
5. PWM not Phase Correct
In phase correct PWM mode, a change from OCRx = TOP to anything less than
TOP does not change the OCx output. This gives a phase error in the following
period.
Problem Fix/Workaround
Make sure this issue is not harmful to the application.
8-bit
Microcontroller
with 16K Bytes
Flash
ATmega161(L)
Rev. E
4. Increased Interrupt Latency
In this device, some instructions are not interruptable, and will cause the interrupt
latency to increase. The only practical problem concerns a loop followed by a twoword instruction while waiting for an interrupt. The loop may consist of a branch
instruction or an absolute or relative jump back to itself like this:
Errata Sheet
loop: rjmp loop
<Two-word instruction>
In this case, a dead-lock situation arises.
Problem Fix/Workaround
In assembly, insert a nop instruction immediately after a loop to itself. The problem will normally be detected during development. In C, the only construct that will
give this problem is an empty “for” loop; “for(;;)”. Use “while(1)” or “do{} while (1)”
to avoid the problem.
3. Interrupt Return Fails when Stack Pointer Addresses the External Memory
When Stack Pointer addresses external memory (SPH:SPL > $45F), returning
from interrupt will fail. The program counter will be updated with a wrong value
and thus the program flow will be corrupted.
Problem Fix/Workaround
Address the stack pointer to internal SRAM or disable interrupts while Stack
Pointer addresses external memory.
Rev. 2473B–AVR–05/02
1
2. Writing UBBRH Affects Both UART0 and UART1
Writing UBRRHI updates baud rate generator for both UART0 and UART1. The baud rate
generator's counter is updated each time either UBRR or UBRRHI are written. Since the
UBRRHI regiSter is shared by UART0 and UART1, changing the baud rate for one UART
will affect the operation of the other UART.
Problem Fix/Workaround
Do not update UBRRHI for one UART when transmitting/receiving data on the other.
1. Store Program Memory Instruction May Fail
At certain frequencies and voltages, the store program memory (SPM) instruction may fail.
Problem Fix/Workaround
Avoid using the SPM instruction.
2
ATmega161(L) Errata
2473B–AVR–05/02
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