Communication

For an introduction to the DSL vocabulary, see Core Concepts.

Modbus send / receive

send writes local values to a remote device. receive reads remote values into local tags.

Target

Define the remote device as a ModbusTcpTarget or ModbusRtuTarget:

peer = ModbusTcpTarget(name="peer", ip="192.168.1.10", port=502)
rtu_device = ModbusRtuTarget(name="sensor", serial_port="/dev/ttyUSB0", device_id=2)

For codegen-only programs (no live simulation), pass a plain string name instead.

Send

with Rung(Enable):
    send(
        target=peer,
        remote_start="DS1",
        source=DS.select(1, 10),
        sending=Sending,
        success=SendOK,
        error=SendErr,
        exception_response=ExCode,
    )

Receive

with Rung(Enable):
    receive(
        target=peer,
        remote_start="DS1",
        dest=DS.select(11, 20),
        receiving=Receiving,
        success=RecvOK,
        error=RecvErr,
        exception_response=ExCode,
    )

Status tags

Both instructions require four status tags:

• sending / receiving (BOOL) — True while the transaction is in progress
• success (BOOL) — True for one scan after a successful transaction
• error (BOOL) — True for one scan after a failed transaction
• exception_response (INT) — Modbus exception code on error

Remote addressing

remote_start can be a Click address string (e.g. "DS1") for Click-to-Click communication, or a ModbusAddress for raw Modbus devices.

For more on the soft-PLC Modbus setup, see Click PLC — ClickDataProvider.