HP 54503A scope, address error - Page 1
Forum section: electronics / testgear

author: iblackford
author_rank: Contributor
timestamp: November 10, 2022, 02:12:16 am
content: Hi All,I have recently acquired an HP 54503A 500Mhz scope. I thought this scope had the standard NVRAM issue, so I replaced it, however the problem still exists.I've attached the picture of this error...I can't find anything in the service manual to isolate this error. Any ideas?Thanks, Ivan

author: iblackford
author_rank: Contributor
timestamp: November 10, 2022, 01:44:19 pm
content: I should add that I _did_ try numerous attempts at holding down a button on startup to attempt a calibration, and nothing was working. I also made sure that the calibration switch was set to unprotected while attempting a calibration.Could this be a ROM/RAM issue? does anyone know where I can find firmware dumps for this or similar models? Schematics?

author: nctnico
author_rank: Super Contributor
timestamp: November 10, 2022, 01:51:03 pm
content: I'd start here. Looks like the 54501A model is related so likely many, if not all information applies to your oscilloscope as well. HP / Agilent has a habit of basing various oscilloscope models on the same hardware platform with only the last digits of the model number being different.http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=HP_Agilent

author: Miek
author_rank: Regular Contributor
timestamp: November 10, 2022, 04:15:34 pm
content: Quote from: iblackford on November 10, 2022, 01:44:19 pmThe "Address Error" a low-level processor exception meaning that the firmware tried to access memory at an odd-numbered address. I would expect the only cause of that to be some corruption happening somewhere, so yeah, I'd suspect bad ROM or RAM.

author: iblackford
author_rank: Contributor
timestamp: November 10, 2022, 04:39:57 pm
content: Cool...thanks, that's what I thought it might be.I'm curious, how did you know that it was an odd address? Is there any further debug information that I can glean from the various numbers on the screen?Thanks, Ivan

author: Miek
author_rank: Regular Contributor
timestamp: November 10, 2022, 05:06:58 pm
content: Just from bits of documentation on 68k series processors:QuotefromCode:http://marc.retronik.fr/motorola/68K/68000/Exception_handling_in_the_68000_[A.CLEMENT_1986_19p].pdfI was pretty sure it's a 68k since most of HP's instruments from that era had one, and looking at the 54501a firmware it has strings for the other standard 68k exceptions (see attachment).It should be possible to glean more information from the numbers on screen (they show the state of various CPU registers at the time of the exception), but it'd require disassembling & reverse-engineering the firmware image.

author: iblackford
author_rank: Contributor
timestamp: November 10, 2022, 05:29:13 pm
content: Thanks for all the help, this is making a lot more sense now. Reading the service manual, I can confirm that it is indeed a 68000. I have a coworker that has done a bunch of bare metal 68k coding in the past, so he may be able to disassemble this and help me out a bit.However, I'm going to start reseating all of the ROM chips first, as they are socketed, and this is something free to try.This scope has sat on a shelf for a couple of years neglected, but I don't remember it having the address error when I diagnosed it back then. I'm hoping that it's not any of the socketed ram chips.Ivan

author: Miek
author_rank: Regular Contributor
timestamp: November 10, 2022, 05:38:06 pm
content: No problemIf you're able to dump the data from the ROMs that would help - they should have a checksum or CRC to test for any corruption in the firmware.

author: iblackford
author_rank: Contributor
timestamp: November 10, 2022, 10:41:42 pm
content: I removed and reseated all the ROMs...and.....Thanks for all the help!

author: nctnico
author_rank: Super Contributor
timestamp: November 10, 2022, 11:40:07 pm
content: Quote from: iblackford on November 10, 2022, 10:41:42 pmCool! Contact problems are the first to look at and typically I start by reseating all chips & connectors. Sorry for not mentioning it.

author: iblackford
author_rank: Contributor
timestamp: November 11, 2022, 01:39:48 am
content: It's on my list of things to check as well, I just figured given that it's such an old and popular unit, maybe there are some folks out there who have experienced corrupt roms or some other age related failure.FYI...if anyone needs a replacement for a DS1230/DS1235 let me know, I rolled my own: