Hi all,

Regarding the RS485 MODBUS port on the PV780T in Powervision 2.6.

If Serial Port 1 is set to Modbus RTU master you gain the ability to have "remote slave devices".

Located in each remote slave device you have the ability to create "Mapping Groups" where you can map all of you modbus registers, and assign variable names etc.

Switching into a modbus read/write scenario. I believe I understand the functionality behind the 4 modbus functions available, (StartRefreshingMappingGroup, StopRefreshingMappingGroup, RefreshMappingGroup, UpdatePort).

If you have 5 read/write modbus registers (say 40001-40005) how do you read all 5 at the same time, and then only write to a single register at a time, say when a number has been entered via keypad (say 40003).

Would you create a single mapping group that reads all the registers at once, and 5 separate mapping groups to write to each of the 5 registers? or is there a better way of doing this?

This would give a total of 6 mapping groups.

I cannot seem to find a way to write to a single register, if there are 5 registers mapped in a single write group.

Also, when is it appropriate to use the Broadcast vs. Remote Slave Device functionality? I cannot seem to find a mention of Broadcast, for modbus, in the user manuals for 2.6.

Please advise.

Ocelot,

Make one group for the 5 registers as a read group. Then make another group as a write group. You can either disable the multiwrite function (function 16) which will force the modbus to write one at a time or you can put one register in one group each. You can put registers in multiple groups and have them linked by unchecking the autocreate variable check box and then choosing the modus register from the variable list.

To do the single writes always, disable function 16.

Let me know if you need more information.

Thanks,

Brian McRae