[Coco] CoCo3FPGA, FPGA Development, and GIME replacement

[Mark McDougall]

On 6/07/2011 3:01 AM, John Kent wrote:

> The DE1 board has an SD card socket on it however implementing an SD card
> interface from the little information I have seen is much harder than
> writing and IDE driver. The IDE driver simply has to set up the sector
> cylinder and head registers issue a read or write command to the command
> register and poll a couple of status bits to see when data is ready on the
> data bus. The issue then is how to interface it to disk BASIC.

I have my Coco 1 implementation running with both CF (r/w) and SD 
(read-only), both via my implementation of the SuperIDE interface. For CF 
(IDE) the implementation is a trivial wrapper around the opencores IDE 
controller (PIO mode only). For SD I implemented an IDE<->SD back-end using 
my colleagues 'parallel-mode' SD controller (reader). They both run HDBDOS.

Accessing SD in SPI mode is quite easy; there's a few cores out there, and 
it's easily fast enough for the Coco. I chose not to only because my 
colleague had written a parallel-mode controller with a much simpler 
interface more suited to being a back-end. I also chose to write an IDE<->SD 
interface so that any system that interfaced to IDE could also be made to 
interface with SD with a simple drop-in back end.

I've got nothing against DriveWire - it's a great piece of work - but I'm 
simply not interested in using it myself.

One of these days - when time permits - I'll start on my Coco 3 
implementation. I'll also hassle my colleague to get write-mode going on his 
SD interface.

Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"