On Tue, May 15, 2012 at 11:45:58PM +0200, email@example.com wrote: >I am not sure if I made myself clear. I want to be able to have a ROM >replacement for the C64 (also other systems but 64 is the starting >point), where I can easily manage what rom image will be made visible >to the system at various addresses. It has to have a piece of own >software too. The one that will display the menus for selection of the >ROM images. After selecting, the images are made visible os ROM areas >to the system and the system is rebooted via cold vector. Basically, you would need a CPLD on the daughterboard that would mimic the PLA and hijack a few addresses for itself. On power-up, the CPLD would initialize its bank selection lines so that the 6510 sees a custom on-board ROM in place of the KERNAL. This custom ROM would display the menu. Once you have selected the combination to use, the custom ROM would write to the CPLD-implemented registers to select the combination and to hide the CPLD register from the 6510 address space. I wrote something like this in the Vic Flash Plugin. It decompresses the ROM images to write-protectable on-board RAM. You might use a simple EPROM for all images, or make some effort to load the ROM images from a SD card. But would it be handy to open the case to switch SD cards? By the way, if you go the CPLD route, why not pick a bigger chip that could implement a co-processor or a REU clone or whatever? Marko Message was sent through the cbm-hackers mailing listReceived on 2012-05-16 07:01:00
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