HP-21MX bootstrapping?

Tim Riker wrote: Just a comment on that, it was written for a requirement similar to yours: to download into the HP machine over a serial line from a modern machine running a terminal program. Please note that the protocol/load format is no relation to the HP Basic-Binary-Loader format: if you wish to use it you'll have to convert your binaries to it's language (tis pretty simple but more work none-the-less). The advantage of it is everything pertinent goes over the serial line in printable ASCII, and it ignores everything else. (It works fine for me but I created all my own support stuff (cross-assembler & simulator) to work with it. As it was written to assemble under my own assembler, there may/will be some minor diffs from the HP asm standards, but the machine code is there in the listing to toggle it in without having to assemble it.) Based on other's responses I suspect you'll find a solution with an original HP loader. Another possibility might be to modify the old HP teleprinter loader: http://www.cs.ubc.ca/~hilpert/e/HP21xx/software/bblteleprinter.html It uses the HP BBL load format. It was for loading over a serial line from the paper tape reader on a teletype, but uses a 12531A IO interface, which was a bit-bang interface. It could be converted for the 12531B/C by, in short, replacing the ReadByte routine with instructions appropriate for the 12531B/C. (Also note that my experience in this is limited to playing with a 2116 system).