HP-42s upgrades



#2

Hi all,

Back in 2004 Nelson M. Sicuro did some work regarding HP-42s mamory upgrade (beyond the the well known 32K RAM expansion)

A reference on his work can be found here.

However, I haven't found any further details on this or any other development in this direction.

Can the extra RAM chip be used for storage?

Does the RAM memory increase by 32k (for a total of 64k)?

Is the ROM chip mapped area (H'20000-H'3FFFF) where the new RAM is placed, accessible for the user?

As everybody can see I'm a complete newbee regarding HP-42s... and a terribly frustrated one (I must add) since I've found that there's no easy way of interfacing with this machine! :-(

Cheers.

Diego.


#3

Here you find some additional information:

HP-42S memory upgrade and overclock

HTH,
Juergen

#4

Hello Diego,

Quote:
Can the extra RAM chip be used for storage?

Yes, but only over the XFCN keyword and additional software interpreting the keyword. The additional software can only get inside over the memory scanner.

Quote:
Does the RAM memory increase by 32k (for a total of 64k)?

No, it doesn't.

Quote:
Is the ROM chip mapped area (H'20000-H'3FFFF) where the new RAM is placed, accessible for the user?

Yes and no, only over the XFCN keyword way.

When you want to simulate the extra memory at H'20000-H'3FFFF you can use Emu42. In normal configuration Emu42 cannot create such a memory configuration, but the additional program MKE42 can. There's a preset called HP42SX in the MKE42.DAT file.

Create such a state file with:

MKE42 myconf.e42 HP42SX

When you want to put data into this area you can use a somewhere hidden function in the debugger.

  1. Call the Debugger under "Tools/Debugger..."
  2. Press the right mouse button (context help) over a data byte in the memory view
  3. There's a menu point "Load Memory Data..."

Some years ago I began with a RS232C interface for the Lewis chip (programmed on a HP28S for easier handling) using the IR-LED port (which is bidirectional). The project still hung at the XMODEM implementation, basic transfer at 2400baud works.

Cheers

Christoph


#5

Hi all,

Thanks a lot for the details. Seems that I still have a long path to learn before I can fiddle with this calc...

However, the refference to the bi-directional IR port sounds really good... Where the supposed receiver photo-transistor is to be placed/connected?

I'll be out for a few weeks... but will try to keep track of this thread.

Best wishes from Zaragoza!

Diego.


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