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Some old school instruments showing how it's done (HP 3325A and Fluke 8506a)

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m k:

--- Quote from: joeqsmith on February 23, 2021, 05:16:31 pm --- And with the power of Google,

--- End quote ---

Like when I couldn't remember witch one the LPT1 address is and tried google.
It wasn't there, I had to change to I/O map and first one didn't even have LPT2.

Maybe Altavista had better SNR.

SilverSolder:

--- Quote from: m k on February 23, 2021, 07:41:15 pm ---
--- Quote from: joeqsmith on February 23, 2021, 05:16:31 pm --- And with the power of Google,

--- End quote ---

Like when I couldn't remember witch one the LPT1 address is and tried google.
It wasn't there, I had to change to I/O map and first one didn't even have LPT2.

Maybe Altavista had better SNR.

--- End quote ---

If you put Google in "Verbatim" mode, it becomes almost usable.

joeqsmith:
Google  "ISA" "printer port" "address"

Second hit was
https://en.wikipedia.org/wiki/Parallel_port

Which states:
Most PC-compatible systems in the 1980s and 1990s had one to three ports, with communication interfaces defined like this:

    Logical parallel port 1: I/O port 0x3BC, IRQ 7 (usually in monochrome graphics adapters)
    Logical parallel port 2: I/O port 0x378, IRQ 7 (dedicated IO cards or using a controller built into the mainboard)
    Logical parallel port 3: I/O port 0x278, IRQ 5 (dedicated IO cards or using a controller built into the mainboard)

If no printer port is present at 0x3BC, the second port in the row (0x378) becomes logical parallel port 1 and 0x278 becomes logical parallel port 2 for the BIOS.

Of course, having used the PC since the start,
debug   - start the debugger
d 40:0  - display the addresses of the printer ports in order

That stuff seems embedded in the memory banks.   :-DD

joeqsmith:

--- Quote from: SilverSolder on February 23, 2021, 07:31:08 pm ---
Yeah, I've also got a "mule" meter for hacking/testing/repairing modules.  I like having at least two of each boat anchor because they can be hard to troubleshoot if you don't have a working one to compare with!

>My guess is that thing is loaded with a lot of 1's and a few 0's sprinkled in the mix.

A remarkably astute guess, you might just be right!  :D

--- End quote ---

Well, I'm at a total loss about U18.  I removed the device without damaging the PCB and installed the same type socket so it looks somewhat the part.   My board uses a DM74S287N.  The programmer supports it no problem but when I read it, the results are very unexpected.  I did reinstall the part and powered up the meter.  No problems at all.   I wonder if this is a problem with my programmer or if this is really the contents as it appears all the bits were set (this part is cleared to all zeros).  If anyone has a programmer that supports it, I would be very interested in knowing if you have the same results. 

When is the last time you heard of Titanium Tungsten Fuses? 

Also, I had mentioned that the cheapo programmer was having a problem with some Lattice GAL22V10Bs.   I tested the parts I thought I may have damaged in the real programmer and no problems.  They erase and program just fine.   So I put them back into the TL866II plus and the problem again repeats, bad pins.  But I noticed that it works correctly the first time every time.  Then I noticed that if I repeat the same process, Read for example, too fast, the pin error happens.  Almost like I am dragging down a supply and it takes time to recharge.   :-DD

SilverSolder:
The file you attached isn't cleared to all zeroes?  Here's what I see in the file, it looks interesting - note the '07' snuck in line 1 and line 9.

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