We're trying to connect a Schwitzer Engineering SEL-3354 to a ABB exciter (not sure of model off the top of my head) and we have the list of tags we want to pull off...

for example...

ABB list shows 40001 as a 16bit entity (not sure if it's called a register or word or what in Modbus language) bit 1 is the exciter status on or off.

We got the cable connected, we turn on the TCP/IP modbus inside the SEL SSNET and it shows connection to the exciter and the exciter is online. So the rough COMM settings should be right...

now in the SSNET for the exciter we can setup different polls and what they do... I would've thought I'd need to setup a poll to read holding register 40001 and then add a "packed DI holding register" tag in the SSNET listing pointing to 40001 bit 1, it doesn't seem to work? Just comes up as bad quality so isn't working at all

The contractor who originally set this up (without a exciter to connect too so this was untested before arriving at site) he has a poll setup to poll not 40001 but simply 1... and his tag looks at word 1 bit 1... the quality of the tag comes up as good but the value we get doesn't make any sense.

We can toggle an alarm in the exciter but we see 3-4 tags the contractor setup in the SEL change values.. and of course none of them are the tag we expected

So there is really something goofy going on here and I'm hoping someone has some experience on setting up a Modbus with one of these Schwitzer Engineer devices and can take pity on me and give some pointers for proper setup. I'm sure once we figure out 1 tag getting the rest will be easy...

 

I know that this is going to sound strange to you BUT to ask for Modicon Modbus Register 40001 you must ask for Modbus Register 0. When you have Modicon Registers listed as 4nnnn you must subtract 40001 in Modbus.

Another example, for clarity, if the Modicon Register were listed as 40109 you must ask for Modbus Register 108.

This is one of those basic things about Modicon Modbus that you need to get used to.