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42073BS-MCU Wireless-09/14

ATmega2564/1284/644RFR2

3.2.19 TST

Programming and test mode enable pin. If pin TST is not used pull it to low.

3.2.20 CLKI

Input to the clock system. If selected, it provides the operating clock of the

microcontroller.

3.3 Unused Pins

Floating pins can cause power dissipation in the digital input stage. They should be

connected to an appropriate source. In normal operation modes the internal pull-up

resistors can be enabled (in Reset all GPIO are configured as input and the pull-up

resistors are still not enabled).

Bi-directional I/O pins shall not be connected to ground or power supply directly.

The digital input pins TST and CLKI must be connected. If unused pin TST can be

connected to AVSS while CLKI should be connected to DVSS.

Output pins are driven by the device and do not float. Power supply pins respective

ground supply pins are connected together internally.

XTAL1 and XTAL2 shall never be forced to supply voltage at the same time.

3.4 Compatibility and Feature Limitations of QFN-48 Package

3.4.1 AREF

The reference voltage output of the A/D converter is not connected to a pin in the

ATmega2564/1284/644RFR2.

3.4.2 Port E6

The port E6 is not connected to a pin in the ATmega2564/1284/644RFR2. The alternate

pin functions as clock input to timer 3 and external interrupt 6 are not available.

3.4.3 Port F3 and F4

The port F3 and F4 are connected to the same pin in the ATmega2564/1284/644RFR2.

The output configuration should be done carefully in order to avoid excessive current

consumption.

The alternate pin function of port F4 is used by the JTAG interface. If the JTAG

interface is used the port F3 must be configured as input and the alternate pin function

output DIG4 (RX/TX indicator) must be disabled. Otherwise the JTAG interface will not

work. The SPIEN Fuse should be programmed in order to be able to erase a program

that accidentally drive port F3.

There are just 7 single-ended input channel to the ADC available.

3.4.4 Port G0

The port G0 is not connected to a pin in the ATmega2564/1284/644RFR2. The

alternate pin function DIG3 (inverted RX/TX indicator) is not available. If the JTAG

interface is not used the DIG4 alternate pin function output of port F3 can still be used

as RX/TX indicator.