Re: Pioneer memory upgrade Message #14 Posted by Christoph Giesselink on 30 Jan 2004, 10:35 a.m., in response to message #7 by Nelson M. Sicuro (Brazil)
> I'm thinking of another "crazyness" about the 42S: I'll try to use the empty space (used with the second ROM in the 17BII) to put *another* SRAM chip, rewire some signals, and try to enable more RAM.
I'm "Mr. Emulation" ;-) and I'm never opened one of my calculators. So this information hasn't verified on a real machine.
In Erik Ehrlings PDF document "A User's Comments on Two HP-42S Emulators" page 6 you see the PCB area of the two extra chips, left the RAM, right the place for the additional ROM.
The question is, can the right place (32KB ROM for HP17B/17BII international versions) can be assembled with a 32KB static RAM?
IMHO yes, it can. The picture show at least four soldering bridges, two for Pin1 (VCC <-> A14) and two for Pin27 (A14 <-> WE/) and these are the differences in the pin layout of 27C256 Eprom (32KB) and a 62256 RAM (32KB). Because there are bridges for RAM selection, we can assume that the IC is also powered in calculator off state.
The address of this memory module is #20000 with a size of 64KB (a 32KB chip is mirrored).
> Any volunteers to create some MCode to test it???
A good entry for this is the free beta version of the Emu42 v0.10beta1. The beta version can only emulate ROM in the area from #20000-3FFFF, so don't try to make a state file with RAM at this position with the MKE42 tool. This only work with my private full version (please no discussions where it is available, it isn't).
But using ROM in our case it perfect, because this allows us to load the additional ROM code at emulator startup. The beta version has also a integrated assembler debugger.
How to get your code into the emulator? The emulator supports packed and unpacked ROM images, the easiest way in our case is to use a copy of the packed ROM image (64KB file size).
Generate your own ASM/RPL code and append the binary data to the end of your ROM image.
Example: copy /b HP42S.ROM.ORG+MYCODE.BIN HP42S.ROM
with
- HP42S.ROM.ORG
copy of the original unmodified ROM image
- MYCODE.BIN
the code we want to append
- HP42S.ROM
resulting ROM code with the name used in the Emu42 KML script
Start Emu42, create a new state file with "File/New..." and you have your code at #20000. The new state file is necessary to configure the MMU with the additional memory controller.
Some words to "some *real* I/O" posted later in this thread. The LED output pin is in "reality" a input/output pin which can controlled by software. I made a demonstration of this feature with a HP28S (use the same chip) at the Allschwil (Switzerland) meeting 2003, emulating a UART with 2400 baud in both directions over the LED pin. Additional hardware (1x OP, 3x Transistors, ...) is required to adjust the signal levels.
Regards
Christoph
http://privat.swol.de/ChristophGiesselink/
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