HP Articles Forum
[Return to the Index ]
[ Previous | Next ]
HP-71B Math RAM
Posted by Marcus von Cube, Germany on 16 Feb 2009, 8:06 a.m.
This is not a typo! ;)
I managed to get the HP-71B Math Pac image into a free RAM port of my real HP-71B. Here is what I did.
The ROM module contains a protected file which will not be copied by the HP-71B's COPY command unless you change the flag beforehand. This is quite easy: Open MATHROM.BIN with a HEX editor and change the byte 03 at address 000E to 00. Voilą, the protection is gone!
In order to save precious RAM you should set the file size in the image to a value that does not include the many 0 nibbles at the end of the ROM: Put the values 50 D8 at address 0014 in the file (original value was D6 FF.)
In EMU71 (with physical HP-71B turned off):
COPY MATHROM:PORT(2) TO :HDRIVE1 CONTROL OFF
On physical HP-71B:
[ON] COPY MATHROM:HDRIVE1 TO :PORT(5.01) SECURE MATHROM [OFF] [ON]
And now to test:
DIM A(5) MAT INPUT A MAT PRINT A
My EMU71 configuration has MATHROM.BIN configured in port 2. I'm pretty sure that you can even leave out the source port specification in the COPY command and EMU71 will still find the file.
I've a CMT card reader port RAM module which installs ports 5.01 to 5.04. 5.01 was just free for the purpose. That's all. If you have claimed all port RAM as main memory, you should be able to copy MATHROM in main RAM but I haven't tested it.
Edited: 5 May 2012, 4:58 a.m.
[ Return to the Message Index ]
Go back to the main exhibit hall