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24228Re: [midatlanticretro] ROM gurus

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  • Dan Roganti
    Jan 31, 2012
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      On Tue, Jan 31, 2012 at 8:55 PM, Dan Roganti <ragooman@...> wrote:




      On Tue, Jan 31, 2012 at 2:17 PM, Mike Loewen <mloewen@...> wrote:

        The 9216 is a 24-pin
      DIP, with dual-active low chip selects, and uses both +5V and +12V.  The
      board these are installed on can use either 9216s or 2716s, but not a mix
      of both.  Here's the info on the ROM board:

      http://bitsavers.org/pdf/hp/terminal/264x/13255-91221_Control_Memory_With_Bank_Select_Module_Oct78.pdf

         Table 4.0 lists the strapping for 9216 vs 2716, and there's a schematic
      at the end.  Any pointers?


      You have to make certain of the CS pin logic levels. Table 4 shows only some kind of DIP switch settings. You like to verify the logic in the schematic where it's used. Just as the firmware is preprogrammed into a Mask Rom at the Factory, these CS pins are also configurable at the factory as either Hi or Lo level inputs by the customer - per their design/schematics. The rest of the chip is straight forward if just you want to read the contents - eg. address, data and power.

      Only these pins are diff from the 2716
          Pin 21= A10
          Pin 20= CS1***
          Pin 19= +12v
          Pin 18= CS1***
      ***check logic level in schematic



      I only looked as far as the page with Table 4, I didn't notice earlier but further in that pdf on page 16, you can see already on this schematic that these Roms are made with Active Lo inputs on both CS pins. I guess that's where you were looking before when you stated this.

      So pins 18 and 20 on these Roms are not an issue, these are the same as a 2716 - ie, Active Lo inputs. You only have to worry about pins 19 and 21 for your adapter.

      =Dan


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