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Modbus error code "-11"


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I'm using USP-070 with UAC-02RSC. I setup two MODBUS masters - one on COM1 (9600 8N2)  and one on the additional port (9600 8E1). For each master I've defined 30 slaves with two periodic operations (period  1 min).

The first modbus line works without any issues however on the second one I'm getting weird results - around half of reads are successful the rest returns status 3. Status of operation is set to -11. I can't find any documentation what it means.

There are no dropped packages, and each slave was double checked to make sure it uses correct transfer params  (9600 8E1). Any ideas what can be wrong, or what -11 means ?


thank you,

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3  =  Connection exists, but there is an error in the MODBUS commands,   -11 = ???

Although it might be a pain to implement, can you try 9600 8N1 on the second line?  And are "half the reads" consistently the same slaves?

And why 8N2 on the first?  Nearly everything I work with Modbus works best at 9600 8N1.  But I acknowledge that's just the gear I work with.  Many of them you can't even change the parity from N.



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@Aus, one of the slaves doesn't allow any transfer mode changes (nothing but ID) ;)

Anyway, issue solved - don't know why but the only solution was to set exactly the same settings on both lines (so 9600 8E1). As of that moment, all started working correctly.

that's a bit odd, tbh as I'd expect UniLogic to either prevent setting two different modes or to handle them correctly.

Wrt -11 - seems, that it was related to an incorrect parity. When changed the parity to a wrong setting on the first line (and disconnected the second line) I got exactly the same error code. 



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