Update on Carte Blanche status.

[Alex Freed <alex_news@mirrow.com>]

There are two main reasons the cards are not in your hands yet apart 
from the manufacturing delays: the emulated disk support was much less 
than perfect and we have discovered a weird unexpected problem - the 
eeprom containing the configuration did not reliably program by using 
the stock Xilinx tools. The process worked most of the time with the 
bigger 500E chips but not with the 250E FPGAs that were supposed to act 
exactly the same according to the Xilinx's documentation.

We had to resolve the second issue one way or the other before shipping 
the boards and ideally I wanted to improve the default configuration 
because there was no easy way to update "it in the field" without extra 
hardware. The cheap parallel port JTAG adapter is only $12 from Digilent 
but using it is not quite trivial.

So I spent the last month designing an easy way to update the 
configuration in the flash eeprom without any extra hardware. I'm happy 
to report a success. I had to completely dismantle the hard-wired SPI 
controller used in the old version and replace that with a very simple 
SPI module controlled by the soft Z80 inside the FPGA. There are several 
consequences of this action:

1. MMC/SD reading is now very reliable even with an SD card that was 
very flaky with the old design. So the NIBBLE mode is more reliable.

2. More importantly we can now re-program the flash with no extra 
hardware from a file on the SD card directly. Takes some 10 seconds and 
didn't fail even once yet out of  5 or 6 times tested.

3. On the negative side there is no direct SPI control by the 6502 any 
more and I did not have a chance to redesign the ProDOS support using 
the new SPI controller.

I feel that (2) is the most important part and since it is now possible 
for the user to update the configuration when new stuff is released we 
should be able to start shipping as soon as we load and test the boards 
with the new configuration.

At the same time the re-configuring is a little dangerous just like 
re-flashing a motherboard BIOS. If something goes wrong during the 
procedure - a power failure or some other malfunction - it can "brick" 
the board and the only way to unbrick will be by using the $12 JTAG 
tool. Or a $300 USB JTAG from Xilinx :)

-Alex.