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Re: Carte Blanche Atto (CB for the IIc)
On 03/27/2011 10:12 AM, Steve wrote:
Hi All,
I havent had the chance to drop in much, but I have been busy
tinkering with II stuff in my spare time. Although its been at a
snails pace, I have managed to prepare a prototype of Carte Blanche
intended for the IIc (called CB Atto). Its a pretty tight fit and
seems to just clear at the moment. There's still a long way to go with
programming etc, but so far it feels like a good start and has passed
all of its tests. I hope to see if Alex has the time to port JAT over
to it at some point. Either way, its been an interesting experimental
board.
Steve,
As always, you do great work!
However, (and please take this as constructive criticism) it would be very
helpful if some of that creative energy went into system documentation for the
original CB. In particular, it's very difficult for a beginner in the field
of HDL and FPGAs to get a foothold on the device. I'm sure all the details
are there, but I would love to see some more high-level discussion of the CB
architecture. For example:
- How does it map to the host bus and what would a basic interface scheme
"look" like in terms of mapping logic to the symbolic port connections?
- Maybe a raw beginner's project that does something simple like embed 6502
code in a ROM area on the FPGA and permit it to be switched in and executed
from the host.
- How does the ASIC adapter map to the FPGA? What would a "framework" that
ties in a device on a that board look like and how are the pin connections
referenced symbolically?
A lot of that information is probably implicit in Alex's designs, the
schematics and the Xilinx databooks, but for the uninitiated the initial
learning curve is quite steep. I've been sitting here with two boards for
over a year and have not been able to negotiate it. I do have a reasonable
amount of background in logic design, but it dates strictly from the TTL 74LS*
era. There are just too many pieces that need to get sewn together at present
for me to get a foothold, and I suspect it's been daunting for some others of
us as well.
Anyway, sorry to sound critical. Maybe it's just me that's dense :-).
Steve