Downloading problems with WiModem 232 and a UDS-10
(03-20-2023, 07:39 PM)admin Wrote: Baud rates have to be same always.  Zmodem bases its timing windows on the baud rate, so it is not surprising you would have a problem.


Well...not necessarily? I mean, the BBS's have always had the ability to negotiate -down- to callers logging in with slower speeds. BBS Express! ST does that now. I mean, I can logon fine at 9600 baud and do everything normally - navigate the menu's, play games, post messages...no problem. Just can't upload or download with Zmodem, but can with Xmodem.

The 8bit people logon anywhere from 1200, 2400, 4800, 9600 and 19.2k. No problem there. Just not able to download anything less than 19.2k with Zmodem.

When we were dialup, you could download at any speed you could logon with and that was with Zmodem. Never seemed to be an issue.

<shrugs> I'm still trying to wrap my head around this stuff and how it seems to have changed these days.  Smile

Thanks as always.
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I think you are a bit confused about how modems work. The modem itself is locked at the EXACT same baud rate on each end. The DTE speed (modem to computer) could be different, and often was in the case of USR Courier modems, but the over-line baud rates HAD to be identical. In fact, the tones you hear as the modems negotiate identify the baud rate on each end and they coordinate the baud rates to be the same.

So, as I said, the actual baud rates on each end MUST be the same for Zmodem to work correctly - or it does exactly what you see. This is because the timing windows are different due to the response speed (based on baud rate). Other protocols do not have any timing windows at all or have extremely long windows where the character times (baud rate) being different does not matter.

If the BBS was set to 9600 baud then anyone calling at 9600 baud would be able to do Zmodem transfers. I can duplicate this exact situation here, and have for many years during testing. Zmodem is very strict on its timing.
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Okay, thanks Jim.
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