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Spartan III Interface

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proacmi2k

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I need to connect spartan XC3S400(3.3) to Tern 5E micro-controller(5V)

my design has three major components.

1. FPGA(3.3V)
2. External FIFO(3.3V)
4. Tern 5E micro controller(5V)

the FPGA continuoesly generates some data and send it to external FIFO(3.3V).

the FIFO status signals are routed through the FPGA to the 5E micro controller.

the 5E micro controller on the basis of the status signal (Half flag), generates clock cycles to retrieve the data from the FIFO.

the 5E send the READ CLCK through the FPGA to the FIFO.

the 5E general Data Bus and Address bus are being read by the FPGA.

FPGA uses the Address bus of 5E to decode and select particular devices.

the 5E databus is bidirectional to the FPGA. some times 5E put data and some times FPGA put data( the output of FIFO through the FPGA to 5E).

this is the system.

so i need to interface FPGA 3.3 IOz to the 5V IOz of 5E ..

both as inputs and outputs.

i have gone through the all the posts on this issue.

i have come to know that FPGA inputs can be made 5V tolerent so just resistors are required.

but since 3.3V VIH/VOL levels are unappropriate for 5V, so there must be
some translators ICS to connect to FPGA outputs to 5E.

i have come across many solutions,
1. Using MAXIM Translators ICS
2. Using PERICOM VOltage level translators.


so : ) after all this details, my simple question or better, request is that,
kindly from your experience, simple suggest me a IC #, its manufacturer,
(Preferrebly the one available from DIGIKEY), thats much reliable and practially used, or what u suggest.



thanks..
plz also make a direct reply to project_acmi@yahoo.com
 

3.3V levels *are* compatible with 5V TTL levels, but I don't know what requirements your microcontroller has (have you checked?).

I also haven't checked the IO specs of the spartan3, but one very simple way to do the conversion if the IOs are fully 5V tolerant is to use 5V pullup resistors and operate the IOs in open-drain mode. Couldn't be simpler/cheaper.

plz also make a direct reply to project_acmi@yahoo.com

Honestly, if you can't be bothered to read the forum...
 

Uhmmm

w@it a sec ...

The spartan3 does NOT handle 5v on its IO lines verry well , even though it has clamp diodes.

You got to shift the 5v to 3v3 levels , and i would do the same the other way ...

/Bingo
 

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