serial line monitor suggestions (HP 4951?)

I need to be able to look at the bits/bytes going back and forth on a serial line. I don't really need to *emulate* anything in particular, like *be* the DTE or DCE, I just want to sniff the line that two other devices are talking on so I can troubleshoot. Besides RS232, I need it to do 422 and maybe 485 (e.g. address filtering). This is for pretty low speeds -- 38400 max and I could even live with just 19200.

The PC-based tool I'm using now just suuuuuucks. At a previous job we had a small standalone HP analyzer which was extremely useful; naturally I don't remember the model name but googling around leads me to think it was an HP 4951x. That model apparently has some storage capabilities -- I don't need that either (just a RAM capture is fine).

Can anyone suggest similar analyzers for this purpose? No SONET, no STP/UTP, just plain old low speed serial lines ... Once I have some models identified then I'll start looking for used units.

Thanks!

Reply to
Chris Campbell
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This might be the PC-based tool you are using, but: see

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. The blurb is still there; if the code isn't still there let me know and I will mail it to you. A couple of outboard converters will let you do 422 and 485. The code doesn't have address filtering but you could probably add it - you'll need a DOS C++ compiler.

Matt Roberds

Reply to
mroberds

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.

Thanks for the response. I really don't want to go with a PC-based solution, as I've been down that road and I know where it ends :) I want something standalone that doesn't require a PC and doesn't require conversion. I need to look directly at the 422/485 lines and that means no PC and no line conversion.

Is an HP4951 going to do this for me?

Reply to
Chris Campbell

At one job, we had an ancient HP serial analyzer and a PC-based one on a laptop. The laptop one didn't work at first, and the HP, despite being ~25 years old at the time, worked fine. I finally futzed with drivers and reinstalls on the laptop for about half a day and got it working well, because I needed to go faster than the 9600 bps the HP could do. So I understand what you're saying. :)

I don't remember the model of that analyzer, but it was from the mid

70s or so. It had a CRT and about a 20-key keypad on the front, not a keyboard. Above the screen, there was a matrix of holes that you would plug gold-plated pins into to set which lines it was monitoring, how the modem control lines worked, etc.

At another job, I used an HP analyzer that was newer - it could store data on a 3.5" 720K? floppy. Pictures from Google (below) tell me that this analyzer was probably newer than a 4951, while the one I talked about above was older.

I don't know if you found this already, but

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has a link to a scanned HP ad at
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, which says the 4951C does 232C and 422A. No mention of 485. Googling on "hp 4951a" and "hp 4951b" also produces useful results, with specifications and a few mentions of units for sale.

Matt Roberds

Reply to
mroberds

Thanks for the excellent links -- this gives me a foothold to start searching with!

Reply to
Chris Campbell

Try the good ol' HP 4952A with the pod for RS-232 and RS-422. There are many pods available (for ISDN too) but I don't remember anything about RS-485. Regards Franco

Reply to
franco.segna

There is a free tool called TALBreakout avbailable at the following URL that should do what you require quite nicely.

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Download the TALBreakout program and read the help file to see how it works. Basically it is designe to run in a PC with two serial ports where you connect the PC in between another PC and a device - i.e. like a breakout box. It then displays everything that goes through the serial line in both directions.

Reply to
Thomas Lutz

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