Logic Levels and Microcontrollers

[elockpicker]

Hi,
I have an Xess board (Spartan 3) which does not support 0-5 Volt logic levels.
Can I use Low Power ATmega microcontrollers to communicate with it ?
Is it just sufficient to set the VCC (of micro) to the appropriate high logic level ?

thank you

 

[farhada]

I believe the IOs of the Xess board powered with 2.5 V, then they should be 3.3V tolerant but not 5V, so if you IOs are 3.3V, then you will be OK.

 

[elockpicker]

thank you ,but are low-power ATmegas applicable ?

 

[farhada]

If you use ATmega128-8 and you power it with 3.3V then you should be OK.

 

[devbisme]

The I/O pins of the FPGA on the XSA-3S1000 Board are powered by +3.3V; the FPGA core logic is running at 1.2V; some ancilliary functions use +2.5V.

You can connect the XSA board to anything that runs on 3.3V.

You can drive external 5V logic if it accepts LVTTL levels: logic 0 < 0.8V and logic 1 > 2.0V.

External 5V logic can drive the XSA board if you place 100Ω to 200Ω in series with the driving pins from the external logic to the pins of the XSA board. These resistors limit the current forced into the pins of the XSA board caused by the 5V-3.3V potential difference.