M
Michael
Guest
Hello everyone,
My project needs quite a bit of RAM (1 MB is enough, more would be nice),
and unfortunately, it needs to interface to a 5V CMOS device (35 inputs, 16
bi-dir, 3 outputs).
Since I'm probably going to need level converting for pretty much any FPGA,
I was thinking why not get a modern high-capacity one that is not even 5V
tolerant. I could probably get away with just using resistors to pull a 3.3
output up to 5V, as the host system will be running under 10 MHz, but I saw
someone mention that clamping diodes aren't active during configuration (at
least on the cyclone). Is this true for most/all FPGA's? I can't prevent
5V signals from getting to the FPGA during configuration, since the 5V
system will be configuring the thing eventually.
My wish list is:
At least 1 MB of RAM (preferably SRAM, since speed and bandwidth aren't a
major factor and its a lot easier than trying to learn how SDRAM works, but
I'm up for a challenge)
5V CMOS compatible I/O's (at least 54 not shared with the SRAM or anything
else)
At least 50 K gates, but speed isn't critical
More of any is of course better, as would be a VGA port, but they're not
essential
Since this doesn't seem to exist, I've been thinking about just getting the
$99 Spartan 3 kit (seems to be a great bargain) and adding on 74LVC4245A's,
but I'd certainly prefer a board with them (or some other conversion
technique) already on. Would this work fine?
Are there any boards affordable to a hobbyist ($200 or less), with something
like a bank of 74LVC4245A's already installed? Other peripherals like VGA
and PS2 are nice but not essential, although they'd let me play with other
things in the future and increase the value of the board a lot.
Sorry for the long post, but I've been doing a lot of research and still
getting nowhere. I plan on designing a custom built board in the end, but I
don't think I could design one properly with my current knowledge, so I want
to get a built, tested board first, and go from there.
--
Michael Noland
My project needs quite a bit of RAM (1 MB is enough, more would be nice),
and unfortunately, it needs to interface to a 5V CMOS device (35 inputs, 16
bi-dir, 3 outputs).
Since I'm probably going to need level converting for pretty much any FPGA,
I was thinking why not get a modern high-capacity one that is not even 5V
tolerant. I could probably get away with just using resistors to pull a 3.3
output up to 5V, as the host system will be running under 10 MHz, but I saw
someone mention that clamping diodes aren't active during configuration (at
least on the cyclone). Is this true for most/all FPGA's? I can't prevent
5V signals from getting to the FPGA during configuration, since the 5V
system will be configuring the thing eventually.
My wish list is:
At least 1 MB of RAM (preferably SRAM, since speed and bandwidth aren't a
major factor and its a lot easier than trying to learn how SDRAM works, but
I'm up for a challenge)
5V CMOS compatible I/O's (at least 54 not shared with the SRAM or anything
else)
At least 50 K gates, but speed isn't critical
More of any is of course better, as would be a VGA port, but they're not
essential
Since this doesn't seem to exist, I've been thinking about just getting the
$99 Spartan 3 kit (seems to be a great bargain) and adding on 74LVC4245A's,
but I'd certainly prefer a board with them (or some other conversion
technique) already on. Would this work fine?
Are there any boards affordable to a hobbyist ($200 or less), with something
like a bank of 74LVC4245A's already installed? Other peripherals like VGA
and PS2 are nice but not essential, although they'd let me play with other
things in the future and increase the value of the board a lot.
Sorry for the long post, but I've been doing a lot of research and still
getting nowhere. I plan on designing a custom built board in the end, but I
don't think I could design one properly with my current knowledge, so I want
to get a built, tested board first, and go from there.
--
Michael Noland