28 Apr
2013
28 Apr
'13
10:44 a.m.
On Apr 28, 2013, at 10:55 AM, ben wrote:
In what sense? The only significant thing (from my POV, for
what that's worth) that the DE0 lacks vs. the DE1 is the
SRAM. It has normal SDRAM (not DDR), which takes a bit of
work to interface, but it's worth the investment in time.
The nice thing about (non-DDR) SDRAM is that it is interfaced
almost identically to regular DRAM, but all the commands and
data come synchronously on a clock edge instead of on the RAS
and CAS edges. The only thing that's pesky (as Sytse pointed
out) is making sure that you have your setup and hold timing
working properly; you'd have to do that anyway with normal
DRAM. DDR gets more hairy, but that's not on the DE0.
Which docs did you have a hard time finding? If you're
looking for some specific topic, I'll be glad to point the
way if I know where it is; I've never found anything to be
particularly hard to find, but if you're not as used to FPGA
design, it might not be as intuitive to know where you're
supposed to be looking. :-)
On 4/28/2013 7:39 AM, David Riley wrote:
Yes, but what makes it incompatible with an IDE cable pinout is
that pins 12 and 30 are ground, 11 is 5v and 29 is 3.3v. On an
IDE cable, 11 is DD3, 12 is DD12, 29 is #DMACK and at least 30
is ground. You need to swizzle the pins around through an
adaptor board if you're going to use it for IDE.
I should point out that those headers aren't
suited for plugging
directly into an IDE drive; the power and ground pins land on
some meaningful data pins. You need to make an adaptor. Also,
avoid using 80-conductor cables with those connectors; those
cables internally bus the IDE grounds together, which don't
correspond to the grounds on the board. You won't short
power to ground or anything like that, but you will lose a few
otherwise useful pins.
A quick glance at the DE0 schematic just shows direct connections
to the headers. On the bright
side, the DE0 and DE1 use the same pinouts for
those connectors, so things should be cross-compatible. The
DE0 even runs some clock pins out there, which can be
pretty useful.
I made a quick choice with the DE0 hoping it would have all what I need.
That was a bad choice on my part, from just reading the web site.
The docs are there, but you have dig for them. None the less, both boards do make nice hardware for
the classic machines.
Indeed! And for other fun little projects.
- Dave