Is the target hardware vintage drives or modern ones? If they are vintage drives (not HD aware/compatible) then you will have to use DD rather than HD media. At least if you want to be able to write t

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Hi Guys - Once I get done building this this FDC, I'll need fresh copies of the MicroDOS and BASIC disks, but my only machine with real floppies has up and died on me. Anyone willing to make me a set

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Found what was the problem. CLEAR line was not connected. Set it to HIGH solve the problem :)

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Hi all, I'm trying to build an 1802 based computer, inspired by Pecom64, which is computer produces in country where I was born. I have problem latching with CDP1852 chip. The one I have is Harris. Th

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That looks cool - thanks!

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From: "Mike McLaren, K8LH" <k8lh@arrl.net> Here's another trick. Since ROM is read-only, you can map write-only I/O (i.e. output ports) into the ROM memory space. This can be useful (for example) as v

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Ok, here's an untested design for inserting both ROM and I/O into the address space... The I/O selector has priority so you could even map I/O into the middle of ROM address space. You can also desele

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Just trying to make sure there is not one of those AH...poo! moments. I should know. My NS* horizon was hit by lightning back in '79 and spent 6 months tracking down all of the failures. I made the er

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Hi Allison - Thanks for the all caps - I fully understand. I'll treat them like the precious icons that they are. Best regards, Todd

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I will repeat myself on one thing... DO NOT PUT THAT DISK IN A DRIVE UNTIL ITS VERIFIED THE SYSTEM CONNECTED AND THE DRIVE ARE WORKING (READS AND WRITES). Sorry for the caps but: Reason is something a

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I think they are the same. Cheers Todd

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How are these different from: https://groups.io/g/cosmacelf/files/MicroDOS

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The basic is RCA 1800 Basic 1 Compiler/Interpreter Manual; MicroDisk CDP18S834V4, supposedly NOS 1982. I'll be picking up this and the MicroDOS disk, CDP18S845, over Christmas. Hopefully they arrived

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Thanks for all of the helpful feedback on the memory addition. I'm getting tired of building low capacity memory cards. Plus I'm running out of sprawl, so I was already thinking about moving forward a

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It's such a simple circuit. Use two of 'em!. One is set to the size and location of the ROM. The other is set to reserve 256 bytes and addressed anywhere else as needed. When placing the hardware, wat

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This 74HC688 method would work well for memory mapped I/O or memory mapped ROM but I'm not sure if it would be helpful if you needed both.

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I second Mike's recommendation for the memory mapping scheme. I am running it on my current SuperElf expander. I've got IDIOT in a 32k EEPROM, mapped at F800-FBFF. All the rest is RAM, in an AS6C1008

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A suggestion for your new memory card, if I may? I realize it's a radical departure from your current design strategy (grin)... Happy Holidays... Cheerful regards, Mike, K8LH

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Hi Chuck - One of the reasons for basing it on the RCA CDP18S651 is so I can use UT71 and RCA MircoDOS intended for the RCA MicroDisk Development System MS2000 - see RCA MPM-241. I managed to find an

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