Hi, On Mon, May 07, 2012 at 06:00:24PM +0200, MichaĹ‚ Pleban wrote: > Hello! > > Working on several hardware add-ons for CBM-II made me thinking > about doing a similar thing for Commodore 64. Specifically, an > ultimate cartridge pack with the following: > > * Small EPROM with bootstrap. > * 16kB RAM. > * SD card interface. > > The bootstrap would load a selected cartridge image from the SD card > into RAM, then reboot the computer to utilize this RAM as cartridge. I also thought about it, since I've started to play with interfacing with SD card on SPI bus, currently only through PC parallel port (to "play" with it and some studies for myself), but I'd use a microcontroller with dedicated SPI capability (btw, I also thought about using ECN28J60 which is a 28-pin SPDIP ethernet controller with SPI bus - it's really cheap, and not so slow, even 20MHz SPI connection is OK for it -, maybe easier to play with it for a hobby user like me, without heavy SMD, etc soldering and PCB designing capaibilities). One question came into my mind however: I would hate to use an EPROM just for bootstrap. It would be interesting to see this works: let's call the program of the microcontroller as "firmware". Now, the firmware would contain some C64 code as well, if C64 needs "bootstrap". The microcontroller on RESET can read it from code memory and write into the RAM. This way, an EPROM is not needed. Just I am not sure it's possible as the time is too short to do this on power up (I mean the C64) and the microcontroller is not ready yet with the copying; but I guess it's possible to stop 6510 (by the uC) till it's done. It's just a side note, that many devices (like real time clock) exists with SPI bus, so many devices (SD card, the mentioned ethernet controller, the real time clock) can be hooked on the SPI bus with seperated CS lines on the microcontroller. This way it gives a great spectrum of purposes without needing a too complex circuit anyway ... Btw, the SD card and eth controller part was the major reason I've asked about the user port on the list, I wanted to interface with an uC (where some SPI devices connected to the uC), since I have not so much experiences yet with using the cartridge port, shame on me :) Message was sent through the cbm-hackers mailing listReceived on 2012-05-07 17:00:34
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