18

2513KS–AVR–07/09

ATmega162/V

Errata

The revision letter in this section refers to the revision of the ATmega162 device.

ATmega162, all

rev.

There are no errata for this revision of ATmega162. However, a proposal for solving problems

regarding the JTAG instruction IDCODE is presented below.

1.

IDCODE masks data from TDI input

The public but optional JTAG instruction IDCODE is not implemented correctly according to

IEEE1149.1; a logic one is scanned into the shift register instead of the TDI input while shift-

ing the Device ID Register. Hence, captured data from the preceding devices in the

boundary scan chain are lost and replaced by all-ones, and data to succeeding devices are

replaced by all-ones during Update-DR.

If ATmega162 is the only device in the scan chain, the problem is not visible.

Problem Fix / Workaround

Select the Device ID Register of the ATmega162 (Either 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. Note

that data to succeeding devices cannot be entered during this scan, but data to preceding

devices can. Issue the BYPASS instruction to the ATmega162 to select its Bypass Register

while reading the Device ID Registers of preceding devices of the boundary scan chain.

Never read data from succeeding devices in the boundary scan chain or upload data to the

succeeding devices while the Device ID Register is selected for the ATmega162. Note that

the IDCODE instruction is the default instruction selected by the Test-Logic-Reset state of

the TAP-controller.

Alternative Problem Fix / Workaround

If the Device IDs of all devices in the boundary scan chain must be captured simultaneously

(for instance if blind interrogation is used), the boundary scan chain can be connected in

such way that the ATmega162 is the first device in the chain. Update-DR will still not work

for the succeeding devices in the boundary scan chain as long as IDCODE is present in the

JTAG Instruction Register, but the Device ID registered cannot be uploaded in any case.

2.

Reading EEPROM by using ST or STS to set EERE bit triggers unexpected interrupt

request.

Reading EEPROM by using the ST or STS command to set the EERE bit in the EECR reg-

ister triggers an unexpected EEPROM interrupt request.

Problem Fix / Workaround

Always use OUT or SBI to set EERE in EECR.

3.

Interrupts may be lost when writing the timer register in asynchronous timer

The interrupt will be lost if a timer register that is synchronous timer clock is written when the

asynchronous Timer/Counter register (TCNTx) is 0x00.

Problem Fix / Workaround

Always check that the asynchronous Timer/Counter register neither have the value 0xFF nor

0x00 before writing to the asynchronous Timer Control Register (TCCRx), asynchronous

Timer Counter Register (TCNTx), or asynchronous Output Compare Register (OCRx).