ATMEGA169 ATMEL [ATMEL Corporation], ATMEGA169 Datasheet - Page 351

• Manufacturer Part Number: ATMEGA169
• Description: 8-bit Microcontroller with 16K Bytes In-System Programmable Flash
• Manufacturer: ATMEL [ATMEL Corporation]

ATmega169 Rev B
2514P–AVR–07/06
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8. Interrupts may be lost when writing the timer registers in the asynchronous
7. Internal Oscillator Runs at 4 MHz
6. LCD Contrast Voltage is not Correct
5. External Oscillator is Non-functional
Interrupts may be lost when writing the timer registers in the asynchronous timer
Internal Oscillator Runs at 4 MHz
LCD Contrast Voltage is not Correct
External Oscillator is Non-functional
USART
ADC Measures with Lower Accuracy than Specified
Serial Downloading
IDCODE masks data from TDI input
Problem Fix / Workaround
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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.
The Internal Oscillator runs at 4 MHz instead of the specified 8 MHz. Therefore, all
Flash/EEPROM programming times are twice as long as specified. This includes
Chip Erase, Byte programming, Page programming, Fuse programming, Lock bit
programming, EEPROM write from the CPU, and Flash Self-Programming.
For this reason, rev-B samples are shipped with the CKDIV8 Fuse unprogrammed.
Problem Fix/Workaround
If 8 MHz operation is required, apply an external clock (this will be fixed in rev. C).
The LCD contrast voltage between 1.8V and 3.1V is incorrect. When the V
between 1.8V and 3.1V, the LCD contrast voltage drops approx. 0.5V. The current
consumption in this interval is higher than expected.
Problem Fix/Workaround
Contrast will be wrong, but display will still be readable, can be partly compensated
for using the contrast control register (this will be fixed in rev. C).
The external oscillator does not run with the setup described in the datasheet.
Problem Fix/Workaround
Use other clock source (this will be fixed in rev. C).
If ATmega169 is the only device in the scan chain, the problem is not visible.
Select the Device ID Register of the ATmega169 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
ATmega169 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 ATmega169 must be the first device in the chain.
ATmega169/V
CC
351
is