AB7817 No Modbus RTU Comm

Anybus Support Anybus Gateways
#1

DeviceNet network configuration was easy. Unable to get RTU to communicate. We have a 4 wire RS485. I have to use a RS422 - RS232 adapter to allow the handshaking and keep our DCS system (Emerson Ovation) from reporting ‘Comm Failure’. Anybus is configured as RS232 and RTU address 1.

I’ve tried different I/O register sizes to get some response. Address overview looks incomplete. Set operation mode screen has ‘Unavailable’.

Seems the Anybus gateway isn’t recognizing the Modbus address poll from Allen-Bradley E3 overloads. Our DCS is requesting device status (word), and phase current (3 integers).

Thanks,

#3

What serial standard is being used just between the master and the slave? Why are you using a RS422 to RS232 converter?

What is the modbus RTU master? Are you seeing any modbus response back?

Network Interface Addendum, Anybus-X Modbus RTU Slave Interface (hms-networks.com)

Deryck

#4

To interface a 4 wire RS485 to your 2 wire connector, I used a RS422/RS232 adapter. I tried changing other wiring, but our DCS faults with a ‘Datalink failure’. I see polling from DCS. This polls 4 AB E3 overloads, requesting status and phase currents (1 word, 3 int). Command from DCS is 3 bits, triggering OUTA, OUTB or Reset.

Let me know if you have wiring method I should try. I’ll see if I can bridge the RS485 send/receive pairs to a 2 wire. There are other links with this setup.

Thanks,

#5

We only support RS485 2 wire or rs232 with this device.

This doesn’t really have enough context for me to understand this. What I would be interested in would be, what modbus requests are being used to query the AB7817 modbus slave interface?
Are you seeing any modbus responses back?

Deryck