ATmega16(L)
succeeding devices of the scan chain. Issue the BYPASS instruction to the
ATmega16 while reading the Device ID Registers of preceding devices of the
boundary scan chain.
–
If the Device IDs of all devices in the boundary scan chain must be captured
simultaneously, the ATmega16 must be the fist device in the chain.
ATmega16(L) Rev. J
• First Analog Comparator conversion may be delayed
• Interrupts may be lost when writing the timer registers in the asynchronous timer
• IDCODE masks data from TDI input
1. First Analog Comparator conversion may be delayed
If the device is powered by a slow rising VCC, the first Analog Comparator conver-
sion will take longer than expected on some devices.
Problem Fix/Workaround
When the device has been powered or reset, disable then enable theAnalog Com-
parator before the first conversion.
2. Interrupts may be lost when writing the timer registers in the asynchronous
timer
If one of the timer registers which is synchronized to the asynchronous timer2 clock
is written in the cycle before a overflow interrupt occurs, the interrupt may be lost.
Problem Fix/Workaround
Always check that the Timer2 Timer/Counter register, TCNT2, does not have the
value 0xFF before writing the Timer2 Control Register, TCCR2, or Output Compare
Register, OCR2
3. IDCODE masks data from TDI input
The JTAG instruction IDCODE is not working correctly. Data to succeeding devices
are replaced by all-ones during Update-DR.
Problem Fix / Workaround
–
–
If ATmega16 is the only device in the scan chain, the problem is not visible.
Select the Device ID Register of the ATmega16 by issuing the IDCODE
instruction or by entering the Test-Logic-Reset state of the TAP controller to
read out the contents of its Device ID Register and possibly data from
succeeding devices of the scan chain. Issue the BYPASS instruction to the
ATmega16 while reading the Device ID Registers of preceding devices of the
boundary scan chain.
–
If the Device IDs of all devices in the boundary scan chain must be captured
simultaneously, the ATmega16 must be the fist device in the chain.
ATmega16(L) Rev. I
• First Analog Comparator conversion may be delayed
• Interrupts may be lost when writing the timer registers in the asynchronous timer
• IDCODE masks data from TDI input
1. First Analog Comparator conversion may be delayed
If the device is powered by a slow rising VCC, the first Analog Comparator conver-
sion will take longer than expected on some devices.
Problem Fix/Workaround
When the device has been powered or reset, disable then enable theAnalog Com-
parator before the first conversion.
17
2466NS–AVR–10/06
ATMEL [ ATMEL ]
