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Thread: Figuring out serial port address and memory map on obscure system?

  1. #11

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    Sleepwalker3: Thanks! I might take you up on you offer eventually, but I think i've figured out enough to get it going.

    What I might do is disable the CPU board memory entirely and have it boot directly from the big memory card. It seems to have the same basic setup as the AMPRO littleboard -floppy interface, but copying the ampro circuit for that WD1772 floppy controller should be doable. the int/ext memory flipflop can just be forced hi or lo by removing the chip from the socket and jumping Q to either VCC or GND.

    I'm not too familiar with the littleboard circuits yet, but aren't they fairly straightforward? O'm gonna use sram instead of DRAM, but aside from that, if i edit IO addresses in ROM, i think it's viable.

    Does anyone know the diff. between the z80 littleboard boot rom and monitor rom?

    thanks!


    Current systems: PDP11/23, ZX-spectrum, MEK-6802D5, Ampex 210 CRT terminal, ZX-spectrum
    Current projects: 8085 Altair 8800 compatible
    Looking for: DEC RX-50 drive, QBUS ROM card, intel 8288

  2. #12

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    Quote Originally Posted by Al Kossow View Post
    stand-alone proms CAN'T have security by the nature of their design.

    internal proms in microcontrollers can, and mostly did as a security measure against reverse-engineering after the first generation or so of parts

    early PLAs, like the 82S100 and 105 also were not protected
    I don't imaging an address decoder would even work with some kind of security. After all, it is suppose to decode addresses on the fly. I could imaging one might require two addresses in sequence to unlock it but more than that I can't imagine much more. It could have a watchdog like function, causing the processor to reset if it got to an undefined address. This might be desired for something like a signal light but still that is a function of the overall circuit and not the security of the decoder itself.
    Dwight

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