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HP Forum Archive 13

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HHP Portable EPROM for HP-41
Message #1 Posted by Jeff on 21 Nov 2003, 8:32 p.m.

I recently purchased a HHP Portable EPROM unit housed in a card reader housing. Upon startup, the unit displays "Working" then says -ALLFAX-. I would like to know more about this unit and the EPROM inserted into it. The unit also came with a Overlay for the HP-41. I have posted at the following address the listing of the functions in this EPROM: http://www.elknet.net/mitchbrent/jdfam/HHPPORTABLEEPROM.DOC If you know any information or are interested in exploring this EPROM with me, please contact me. Best Regards, Jeff

      
Re: HHP Portable EPROM for HP-41
Message #2 Posted by Emmanuel, France on 22 Nov 2003, 3:13 p.m.,
in response to message #1 by Jeff

Dear Jeff,
Your HHP Portable Eprom is a 32K Eprom Box.

You can only have 4 size configurations:
4K (one 2764 for L8 & one 2732 for U2)
8K (one 2764 for L8 & one 2732 for U2)
16K (one 27128 for L8 & one 2732 for U2)
32K (one 27256 for L8 and one 2764 for U2)
2732, 2764, 27128 and 27256 are Eproms.

You have 2 DIP switches:
one for memory size & L8 chip type
one for port address

When you open your HHP-PE (remove the 4 screws on HP-41 side), you have something like that:

 --------------  
|   ________   |
|  |   L8   |  |
|  |________|  |
|              |
|  |1 2 3 4 |  |_______
|                      |
|  |1 2 3 4 |          |
|   ________           |
|  |   U2   |          |
|  |________|   _______|
|______________|

The top DIP switch defines the memory size and L8 type of chip used as shown in the table below.

The bottom DIP switch defines the port address desired for the Eprom memory.

    MEMORY SIZE   L8 CHIP TYPE
SW   1   2   3         4
    --- --- ---       --- 
4K   +   +   +    + for 2764
8K   -   +   +      or 27128
16K  -   -   +
32K  -   -   -    - for 27256

            PORT  ADDRESS
SW          1   2   3   4
           --- --- --- ---
port 1      -   +   +   +
port 2      -   +   -   +
port 3      -   -   +   +
port 4      -   -   -   -

SW for switch
+  for up
-  for down

To be continued...

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