Date: 2004-06-15 08:42:45
Hi All, Well, having finally proven out my DRAM refresh scheme for internally mounted 1, 4 or 16MB SIMMs on the weekend, I'm very close to finalising the hardware side of this project. A bit of a project overview is given below, but the main question I have at the moment is where to map in the control registers I need. A logical choice for me is in the VIC I/O space (because the device will be a VIC socket plug in), new registers $D03E and $D03F. I'm looking at these registers being Write-Only so I can save some decode logic. The original Transactor design used the $01 port, but I need more bits than are available and this location does have some compatibility issues (GEOS's calculator is one such example). The questions I have are: 1) Will the VIC definitely ignore these writes (I presume it will not address wrap and write to some existing VIC register) 2) Will a SuperCPU be able to write to this location (I am guessing that it just writes through to all registers which are not its own special CPLD). I want this expansion available to those users too. I don't have a SuperCPU to check... 3) Is there any other expansion which might already use these two registers (I think the C65 had some extra registers.... what about the C-1) Any comments appreciated. - Nick Project Overview: * 30pin SIMM based RAM expansion (1Mb, 4Mb, 16Mb) * Hidden refresh scheme * Common memory approach similar to C256 of Transactor design * Single board plug-in replacement for VIC (original VIC gets PiggyBacked) plus some jumper clips for extra address lines * Control registers in VIC I/Ospace * All logic integrated into a single CPLD (44pin) * Internally addressible - available for VIC graphics and usable by external processors also. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Your Engineering Solutions Provider http://www.orbeng.com.au/orbital/engineeringServices/engServices.htm - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - PLEASE TAKE NOTE: The contents of this email (including any attachments) may be privileged and confidential. Any unauthorised use of the contents is expressly prohibited. If you have received this email in error, please advise us immediately (you can contact us by telephone on +61 8 9441 2311 by reverse charge) and then permanently delete this email together with any attachments. We appreciate your co-operation. Whilst Orbital endeavours to take reasonable care to ensure that this email and any attachments are free from viruses or other defects, Orbital does not represent or warrant that such is explicitly the case (C) 2004: Orbital Engine Company (Australia) Pty Ltd and its affiliates Message was sent through the cbm-hackers mailing list
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