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HP Forum Archive 14

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HP-85 ROM Pin Configurations
Message #1 Posted by JeffD on 13 Oct 2004, 7:41 p.m.

Does anyone know what the pin configurations are for the HP-85 ROMS? Is there any documentation to describe how the HP-85 communicates with the ROM modules? It would be an interesting project to develop a "programmable ROM drawer" but possibly hold many ROM images like the MLDL2000 or clonix. Please let me know if you have ever seen documentation for such or have successfully built one.

      
Re: HP-85 ROM Pin Configurations
Message #2 Posted by Vassilis Prevelakis on 14 Oct 2004, 4:56 a.m.,
in response to message #1 by JeffD

The circuit diagrams of the HP-85 are included in the service manual of the HP-85 in the MoHPC CDROM collection.

Here are the option ROM pinouts:

   ___________________
  /                   \
  | BX4           BX3 |
  | BX5           BX2 |
  | BX6           GND |
  | BX7           BX1 |
  | -RC           BX0 |
  | VGG (+12V)    VBB | (-5V)
  | VDD (+6V)    -WrX |
  | f12 (phi 12) -RdX |
  | f21 (phi 21) -LMAX|
  | f1 (phi 1)   -PWO |
  | f2 (phi 2)   -PWO |
  |___________________|

PWO: Power On Signal
LMA: Valid Address on Bus
Rd:  Read Data
Wr:  Write Data
RC:  ???

      ____                    ____
      |   |                   |   |
      |   |                   |   |
f1:  _|   |___________________|   |__________________________

            ____                     ____
            |   |                    |   |
            |   |                    |   |
f12: _______|   |____________________|   |___________________

                  ____                     ____
                  |   |                    |   |
                  |   |                    |   |
f21: _____________|   |____________________|   |_____________

                        ____                     ____
                        |   |                    |   |
                        |   |                    |   |
f2:  ___________________|   |____________________|   |_______

Note that the logic is 6V and the clocks are 12V !!!

The ROM pinouts are all the same, the ROM socket pins are also all the same. Each ROM selects itself if it sees its id . This is the reason that if you plug two (say) I/O ROMS, you may damage your HP-85.

**vp

            
Re: HP-85 ROM Pin Configurations
Message #3 Posted by JeffD on 16 Oct 2004, 10:13 p.m.,
in response to message #2 by Vassilis Prevelakis

Would the 2708 EPROM work? It has the 12V, -5V but it only has a +5v. The spec states that that it would accept 5.25v max. Do you know of an EPROM that would compare to this HP-85 specification? Thanks, Jeff

                  
Re: HP-85 ROM Pin Configurations
Message #4 Posted by Vassilis Prevelakis on 16 Oct 2004, 11:44 p.m.,
in response to message #3 by JeffD

JeffD wrote:
> Would the 2708 EPROM work?

Sorry, the HP ROMs have a lot of logic built into them. They are rather comparable to the HP-41 ROMs where you actually need a microcontroller to emulate the ROM.

Alternatively you may use a programmable ROM drawer (HP 82929A)

http://www.series80.org/Manuals/HP82929A.pdf

Unfortunately they are rather rare and fetch a high price on eBay (latest one went for $159.25, http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5128991233)

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