Posts: 304
Threads: 32
Joined: Nov 2005
Here you find some additional information:
HP-42S memory upgrade and overclock
HTH,
Juergen
Posts: 355
Threads: 67
Joined: Nov 2005
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.
- Call the Debugger under "Tools/Debugger..."
- Press the right mouse button (context help) over a data byte in the memory view
- 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