Re: Diagnostic ROM for 71B Message #9 Posted by Eric Smith on 3 June 2005, 10:20 p.m., in response to message #7 by J-F Garnier
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The Diagnostic ROM may be a true take-over ROM, as the port 1 includes the OD signal to disable the internal ROMs.
The HP-71B Service Manual states that the diagnostic ROM must be used in port 1.
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Using a logic analyzer to the Saturn bus will not be so easy, because you will have to disassemble the bus commands to decode address and so on,
Not a problem. I've written program to decode logic analyzer traces from other HP calculators, as well as from many other things. I also recently needed to be able to use a waveform viewer for logic analyzer dumps. There's a standard digital waveform file format, VCD ("Value Change Dump"), so I wrote la2vcd to convert the files from my HP 16500B.
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and you may not sure that all addresses are fetched.
If it's like other HP diagnostic ROMs, it will have the
ability to check itself, by computing a checksum.
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An other way would be to use a small assembly language routine running in RAM to copy the content into a 32k independant RAM.
That's been suggested. But if I'm not mistaken, as soon as you try to plug in the diagnostic module, you'll get a non-maskable "module pulled" interrupt, and the vector is in the ROM.
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