HP Forum Archive 06

[ Return to Index | Top of Index ]

Questions on HP 41 MLDL Message #1 Posted by Juergen Rodenkirchen on 29 June 2001, 8:10 p.m. Hi evereybody! Lately, I've got an HP 41 MLDL which is an "home made device". I think it works very similar to the "Eramco" type of MLDL. Anyway, I've absolutely no idea how to get it work, hence I'm desperately looking for somewhat like a manual. Can anyone help me? In particular, the MLDL came with EPROMS called L- and U-EPROMS; What does the mean? There are 2 EPROMS called "EQ DAVE"; are those "DAVE ASSEM" EPROMS enabling one to use mnemonics from the keyboard? I'd appreciate any kind of help or information. Regards, Juergen

Re: Questions on HP 41 MLDL Message #2 Posted by Tony Duell on 29 June 2001, 8:40 p.m., in response to message #1 by Juergen Rodenkirchen The HP41 machine code instructions are 10 bits long (note, it's not strictly microcode IMHO). Most common EPROMs are 8 bits wide, so you can't store an HP41 instruction in a single location of a normal EPROM. Waht was normally done was to have pairs of EPROMs, The 'L' (lower) one stored the bottom 8 bits of each instruction. The 'U' (upper) stored the top 2 bits. Noramlly, the 'U' EPROM stored the top 2 bits of 4 instructions packed into a single (8 bit location), so only a quarter as many locations were used in this chip than in the lower one. That's why the EPROMs are often different sizes (e.g. a 2732 4K chip for the lower bits and a 2716 2K chip (only half of which was used) for the upper bits). As regards what's in your EPROMS, what happens if you plug it into an HP41 and do a CAT 2? Does it show up at all?

Re: Questions on HP 41 MLDL Message #3 Posted by Chris Catotti on 2 July 2001, 12:32 p.m., in response to message #2 by Tony Duell There was a write-up about the DAVID ASSEMBLER in a PPC Journal. If you need a copy of the article, and if you would like a copy of the DAVID ASSEMBLER keyboard overlay, drop me an e-mail with your mailing address and I'll send you a copy.

[ Return to Index | Top of Index ]

Go back to the main exhibit hall