Replacing Wonderware InTouch 7.1 & Motorola MOSCAD

[SFTP-ChZeman]

We currently run Wonderware 7.1(1?) interfaced to a Motorola MOSCAD(?) unit using RS232 that talks to a number of sites with I/O modules to control lighting and monitor fire systems, etc. We want to phase out the Motorola units with PLCs in the field. We already have a PLC talking to an MQTT server and everything between FUXA and our test PLC is working great. Unfortunately, we can't just replace all the Motorola units with PLCs in one go and need to operate both while we phase the old system out.

I imagine it would be easy enough to interface using MODBUS RTU. I'm just wondering if anyone else here has done it.

As far as configuring the tags, each I/O module in the field is assigned a MODBUS address and each device assigned to a single bit of that address. For example, a switchbuilding's fire panel is assigned 306146:01 (address 306146, bit 1) and a another fire panel 306146:02. What I can't figure out, since I don't know a lot about MODBUS and the FUXA documentation is lacking in this area, is how to configure my tags. Do I create an Int32 tag that I map bits of to other tags representing the field devices or is the "Divisor" field where I specify the bit of word? I'm lost here.

Thank you,
Chris