Which chip should I use?

Hello,

I need an FPGA chip which fulfills the following constraints:

-- it has at least 64 IO lines;
-- it is not very fast, 133MHz is the highest possible internal frequency;
-- it contains about 500--1000 LE;
-- very important: it can directly communicate with 5V TTL devices,
this means that its inputs are 5V-tolerant, or better: its V_io = 5V;
-- the software can be easily obtained and is cheap or even free,
so perhaps only Altera and Xilinx should be considered as possible
vendors;
-- it is relatively cheap;
-- built-in configuration memory would be a great feature (because of 
piracy).

What would you recommend me?

    Best regards
    Piotr Wyderski

Piotr Wyderski wrote:

> Hello,
>
> I need an FPGA chip which fulfills the following constraints:
>
> -- it has at least 64 IO lines;
> -- it is not very fast, 133MHz is the highest possible internal 
> frequency;
> -- it contains about 500--1000 LE;
> -- very important: it can directly communicate with 5V TTL devices,
> this means that its inputs are 5V-tolerant, or better: its V_io = 5V;
> -- the software can be easily obtained and is cheap or even free,
> so perhaps only Altera and Xilinx should be considered as possible
> vendors;
> -- it is relatively cheap;
> -- built-in configuration memory would be a great feature (because of 
> piracy).
>
> What would you recommend me?
>
>    Best regards
>    Piotr Wyderski
>
5V tolerant and cheap are mutual exclusive. You can use series resistors 
to make the input 5V tolerant or use some "Quick Switches" in series.
Regards
Thomas

"Piotr Wyderski" <wyderskiREMOVE@ii.uni.wroc.pl> writes:
> I need an FPGA chip which fulfills the following constraints:
> -- it has at least 64 IO lines;
> -- it is not very fast, 133MHz is the highest possible internal frequency;
> -- it contains about 500--1000 LE;
> -- very important: it can directly communicate with 5V TTL devices,
> this means that its inputs are 5V-tolerant, or better: its V_io = 5V;
> -- the software can be easily obtained and is cheap or even free,
> so perhaps only Altera and Xilinx should be considered as possible
> vendors;
> -- it is relatively cheap;
> -- built-in configuration memory would be a great feature (because of
> piracy).

Xilinx Spartan 2 for all but the last requirement.  The last two
requirements are mutually exclusive.

Thomas Rudloff wrote:

> 5V tolerant and cheap are mutual exclusive.

Well, it is undoubtedly true if we consider all modern devices,
but here the chip can be a little outdated -- it will work as an
IDE interface (UltraDMA 133, two channels) and perform some
auxilary tasks. The power consumption is not very important.
Does it help?

> You can use series resistors to make the input 5V tolerant

Not at this speed, I think. A column of some LVX translators
(74LVX245, for example) would be much better, but the board
sould be as small as possible, so I don't want this approach.

> use some "Quick Switches" in series.

Hm, what are they?

    Best regards
    Piotr Wyderski
 

Piotr Wyderski wrote:

> Thomas Rudloff wrote:
>
>> 5V tolerant and cheap are mutual exclusive.
>
>
> Well, it is undoubtedly true if we consider all modern devices,
> but here the chip can be a little outdated -- it will work as an
> IDE interface (UltraDMA 133, two channels) and perform some
> auxilary tasks. The power consumption is not very important.
> Does it help?
>
>> You can use series resistors to make the input 5V tolerant
>
>
> Not at this speed, I think. A column of some LVX translators
> (74LVX245, for example) would be much better, but the board
> sould be as small as possible, so I don't want this approach.
>
>> use some "Quick Switches" in series.
>
>
> Hm, what are they?
>
>    Best regards
>    Piotr Wyderski
>
Have a look at http://www.idt.com/?id=34 the "Quick Switches" were 
invented by "Quality Semiconductor".
There should be an App Note how to use them as bus translator.

Maybe a CPLD instead of an fpga may be a better choice in your case.

Regards,
Thomas

Thomas Rudloff wrote:

> Have a look at http://www.idt.com/?id=34 the "Quick Switches" were 
> invented by "Quality Semiconductor".

Thanks, they look nice. :-)

> Maybe a CPLD instead of an fpga may be a better choice in your case.

Hm, I don't think so, large (512+ cells) CPLDs are very expensive.
But an ACEX FPGA seems to be a reasonable candidate (250MHz,
5V-tolerant, available in the TQFP100 and TQFP144 packages and
they have more than enough cells). FLEX6K are good too.

    Best regards
    Piotr Wyderski

Piotr,

A single chip solution that has 5v tolerant I/Os is the XPGA125 device
from Lattice.  This is an sram device with integrated E2 memory, so the
device is totally secure.  You can download the sw for free.
http://www.latticesemi.com/products/fpga/xpga/index.cfm
The newer XP device is not 5v tolerant, but more cost effective and
still
non volatile.  Either way both devices are fully secure &
reconfigurable.

Piotr Wyderski wrote:
> Hello,
>
> I need an FPGA chip which fulfills the following constraints:
>
> -- it has at least 64 IO lines;
> -- it is not very fast, 133MHz is the highest possible internal
frequency;
> -- it contains about 500--1000 LE;
> -- very important: it can directly communicate with 5V TTL devices,
> this means that its inputs are 5V-tolerant, or better: its V_io = 5V;
> -- the software can be easily obtained and is cheap or even free,
> so perhaps only Altera and Xilinx should be considered as possible
> vendors;
> -- it is relatively cheap;
> -- built-in configuration memory would be a great feature (because of

> piracy).
>
> What would you recommend me?
> 
>     Best regards
>     Piotr Wyderski

Hi Piotr,

>> Maybe a CPLD instead of an fpga may be a better choice in your case.
>
> Hm, I don't think so, large (512+ cells) CPLDs are very expensive.
> But an ACEX FPGA seems to be a reasonable candidate (250MHz,
> 5V-tolerant, available in the TQFP100 and TQFP144 packages and
> they have more than enough cells). FLEX6K are good too.

If you are willing to use resistors/translator on inputs, you can also 
consider Altera's Max II family (specifically the EPM1270 in this case). 
You've stated a "133 Mhz" operation requirement, but the speed of operation 
is a combination of what your design is doing and the speed of the device. 
I'm sure you know this, but even though an ACEX can be clocked at 250 Mhz 
doesn't mean all designs will run that fast.  The EPM1270 gives you 1270 
4-input logic elements, integrated configuration memory, and very high 
operating speeds.

Good luck,

Paul Leventis
Altera Corp. 

Paul Leventis (at home) wrote:

> If you are willing to use resistors/translator on inputs, you can also 
> consider Altera's Max II family (specifically the EPM1270 in this case).

Well, 2 IDE channels require ~64 buffered IO lines and it means 8
additional LVX245 chips, what makes the board considerably larger
and increases the cost by about 2$ (low cost is a priority in this design).
Resistors would be good, because they are small and cheap, but
I don't believe that they will perform their job well at this speed.

> You've stated a "133 Mhz" operation requirement, but the speed of 
> operation is a combination of what your design is doing and the speed of 
> the device.

Of course, but here the design can be easily pipelined, so the chip
doesn't have to be extremely fast just to compensate a wrong algorithm.

> The EPM1270 gives you 1270 4-input logic elements, integrated
> configuration memory, and very high operating speeds.

But it cannot work with 5V devices. :-(

    Best regards
    Piotr Wyderski

Piotr Wyderski wrote:
> Thomas Rudloff wrote:
...
>> use some "Quick Switches" in series.
> 
> Hm, what are they?
> 
>     Best regards
>     Piotr Wyderski

Piotr,

check out the SN74TVC3010 from TI. It's a 10 channel voltage
level converter. We use them to interface 5 Vdevices to 3.3V
FPGAs. Works like a charm, and 133 MHz should be no sweat either ...

DigiKey lists them for about $1.10 each (qtty 25)

Best Regards,
rudi
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