ROCLINK800 Floboss 107 MODBUS Slave configuration


Thread Starter


Fairly new to dealing with flow computers in general (been a steep learning curve). We have a brand new Floboss 107 unit installed and initially configured it using the ROCLink software. For a longer story short, we have a cellular backhaul unit with MODBUS passthrough (there are other modbus enabled devices connected to it, whose addresses can be change to avoid interference with the Floboss addressing). "passthrough" in this sense is if the address doesn't exist on the backhaul unit, it passes it on through its RS-232 port which is connected to COM2 on the Floboss 107 (19.2k 8N1; ASCII mode).

Now I initially attempted to configure the floboss with ROCLink as a MODBUS slave, and picked the registers and assigned address numbers (ie. Total Flow Today - start address 1, end address 2, type parameter; Instantaneous Flow - start address 3, end address 4, type parameter; etc..). I've futzed around with various settings, but I seem unable to configure this correctly. Looking though the docs (unless im missing a whole sheet), I only seem to find information on setting it up as a MODBUS master with custom User Programs (something that I don't need).

Anyone have a quick tutorial per-se on a simple setup like this? (link, text, missing docsheet heh) Thanks for any help!
Hi my friend,

i got just the same problem but i use a MVI56E-MCM Card for Controllogix PLC´s series. i just don´t find the correct configuration. if you solve your problem plis let me know how. i´ll do the same if a figure out how solve mine.

best regards
I got the same problem with flobos 103 and micrologix 1400.

I have been able to read the modbus data but it's different with the actual data.

Is there any conversion or calculation that had to be done?

thanks in advance
The parameters you are requesting are IEEE Single Precision Floats which come out in one of four byte orders depending on the "Conversion Code". The four byte orders are:

Conversion 65 - B0 B1 B2 B3
Conversion 67 - B1 B0 B3 B2
Conversion 69 - B2 B3 B0 B1
Conversion 71 - B3 B2 B1 B0

Randy Sirois


I am trying to do the same thing using the 1400 B-Series and a Floboss-107 and I'm not having much luck. How did you set up your Floboss and your messaging in the 1400?

I have set a few FB 107's up as Modbus slaves. The following should work for you:

-I use Conversion code 66

-The registers are offset by 1 in the FlowBoss. If you want to assign 40001 and 40002 to the Flow Today value, it is enter as a Start Register of 0 and an End Register of 1 in the FlowBoss (in the Modbus Register Screen). Most people make the mistake of entering 40001 and 40002, which returns an error code.

I hope this helps,