PLC & Machine ConnectivityPLCs, drives and counters to your MES or cloud — with a local HMI and remote SCADA on the same gateway
The gateway polls your PLC and drives over Modbus RTU — or Modbus TCP on the WT460M and WT600M — and publishes named tags to your MES or cloud. A local HMI can read the same values from the gateway, a fault bit in the PLC's status word can text the line engineer, and your SCADA can reach the PLC through the gateway when it needs to.
Step 1 of 5The gateway polls the PLC and the drive on the RS-485 line and counts the product sensor's pulses on its own input.
Step 2 of 5Named tags — line state, speed, count — go to the MES as JSON over MQTT on the log interval.
Step 3 of 5The local HMI reads the same values from the gateway, which answers as a Modbus slave (WT460M, WT600M). The PLC is polled once, not twice.
Step 4 of 5The PLC sets the emergency-stop bit in its status word. A rule on that one bit fires once and texts the line engineer.
Step 5 of 5Remote SCADA sends a raw Modbus frame over the second server link. The gateway passes it to the PLC untouched and returns the reply — transparent mode on the WT460M.
Field dataTo your serverSMS from the gatewayCommand / write
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What connects to the gateway
EquipmentHow it connectsWhat the gateway reads
PLC with a Modbus slave portRS-485 · Modbus RTUHolding and input registers, coils and status words, each named as a tag
PLC or meter on the plant networkEthernet · Modbus TCP (WT460M, WT600M)The same register types over the LAN, polled alongside the RS-485 devices
Variable-frequency driveRS-485 · Modbus RTUFrequency, current, run state and fault code
Product counter or proximity sensorPulse-rated inputCount and rate, set or cleared remotely
Local HMI or SCADAReads the gateway as a Modbus slaveThe gateway's copy of the readings, over TCP or RS-485 (WT460M, WT600M)
Digital and relay I/OWT32i card on RS-485Ten digital inputs and eight outputs as Modbus coils
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What the gateway does here
Modbus masterYour PLC's registers, as named tagsUp to 64 devices and 3,000 registers on PRO and MAX. Each register is named the way your MES should see it, with its type, word order and scaling.
Two serversMES and remote SCADA side by sideThe primary server always gets the polled data; the second takes the same data or — on the WT460M — carries SCADA's raw frames in transparent mode.
Modbus slaveOne poll serves the HMI and the cloudOn the WT460M and WT600M a local HMI or SCADA reads the gateway itself, over TCP or RS-485, so the PLC is not polled twice.
Edge triggerAct on one fault bitA rule picks one bit of the PLC's status word and fires once when it turns on: an SMS from the gateway's SIM, a Modbus write, or the relay.
Remote writesSetpoints from the serverA JSON command or a raw Modbus frame from your server reaches the PLC through the gateway — writes by register name or address.
Store & forwardShift data with no gapsCounts and states logged while the link is down go out oldest first, with their own time stamps.
Modbus, not every fieldbusThe gateways speak Modbus RTU and Modbus TCP. A PLC that offers only EtherNet/IP, PROFINET or S7 needs a Modbus port, card or server block in its program first.
Writes move machinesA remote write changes a running machine. Keep the interlocks in the PLC, and let the server write only the setpoints the PLC is built to accept.
Transparent mode reaches the RS-485 slavesToday SCADA's raw frames are carried to the devices on the gateway's RS-485 line. A Modbus TCP device behind the gateway is reached by polling.
Supervision, not a control loopA cellular round trip takes hundreds of milliseconds and sometimes seconds. Use the link to watch and to send supervisory commands, not to close a control loop.
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Questions
Can the gateway read my PLC?
If the PLC has a Modbus slave port — Modbus RTU on RS-485, or Modbus TCP on the WT460M and WT600M — yes. Registers, coils and status words are read and named as tags. Siemens S7, EtherNet/IP and PROFINET are not spoken directly; the PLC needs a Modbus option first.
Can a local HMI and the cloud both use the readings?
Yes, on the WT460M and WT600M. The gateway polls the PLC once, sends the readings to your servers, and answers a local HMI or SCADA as a Modbus slave over TCP or RS-485.
Can our SCADA reach the PLC remotely?
Yes, on the WT460M: its second server link can run in transparent mode, carrying SCADA's raw Modbus frames to the RS-485 devices and returning the replies untouched, while the primary server keeps receiving the polled data.
Can the server change a setpoint in the PLC?
Yes — a JSON command or a raw Modbus frame from the server is written to the PLC through the gateway. Keep the PLC's own limits and interlocks in charge of what a written value may do.
How many tags can one gateway handle?
Up to 3,000 registers from up to 64 devices on the PRO and MAX series (1,800 from 32 on LITE), named and typed in the gateway's Modbus database.
Will it alert us when the machine faults?
Yes, on the PRO and MAX series. A rule on one bit of the PLC's status word fires once when the bit turns on, and can send an SMS (4G models), write to a device or switch the relay.
