AT32UC3L064_10 Datasheet, PDF (75/88 Pages) ATMEL Corporation – 32-bit AVR®Microcontroller

10.4.8 AST
10.4.9 WDT
32099DS–06/2010
AT32UC3L016/32/64
None.
18. GCLK5 is non-functional
GCLK5 is non-functional.
Fix/Workaround
None.
19. DFLLIF might loose fine lock when dithering is disabled
When dithering is disabled, and fine lock has been acquired the DFLL might loose the fine
lock resulting in a up to 20% over-/undershoot.
Fix/Workaround
Solution 1: When the DFLL is used as main clock source the target frequency of the DFLL
should be 20% below the maximum operating frequency of the CPU. Don’t use the DFLL as
clock source for frequency sensitive applications.
Solution 2: Do not use the DFLL in closed loop mode.
20. PCLKSR.OSC32RDY bit might not be cleared after disabling OSC32K
In some cases the OSC32RDY bit in the PCLKSR register will not be cleared when OSC32K
is disabled.
Fix/Workaround
When re-enabling the OSC32K, read the PCLKSR.OSC32RDY bit. If this bit is:
0: Follow normal procedures.
1: Ignore the PCLKSR.OSC32RDY and ISR.OSC32RDY bit. Use the Frequency Meter
(FREQM) to determine if the OSC32K clock is ready. The OSC32K clock is ready when the
FREQM measures a non-zero frequency.
1. AST wake signal is released one AST clock cycle after the BUSY bit is cleared
After writing to the Status Clear Register (SCR) the wake signal is released one AST clock
cycle after the BUSY bit in the Status Register (SR.BUSY) is cleared. If entering sleep mode
directly after the BUSY bit is cleared the part will wake up immediately.
Fix/Workaround
Read the Wake Enable Register (WER) and write this value back to the same register. Wait
for BUSY to clear before entering sleep mode.
1. Clearing of the WDT in window mode
In window mode, if the WDT is cleared 2^TBAN CLK_WDT cycles after entering the window,
the counter will be cleared, but will not exit the window. If this occurs, the SR.WINDOW bit
will not be cleared after clearing the WDT.
Fix/Workaround
Check SR.WINDOW immediately after clearing the WDT. If set then clear the WDT once
more.
2. VERSION register reads 0x400
The VERSION register reads 0x400 instead of 0x402.
Fix/Workaround
None.
3. Clearing the Watchdog Timer (WDT) counter in second half of timeout period will
issue a Watchdog reset
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