Panasonic MEWTOCOL

The MEWTOCOL module targets Panasonic FP-series PLC communication over MEWTOCOL-COM ASCII. It supports %NN# station frames, BCC checks, DT/LD/FL data registers, X/Y/R/L contact words, point acquisition, write-back by point name, and virtual PLC simulation.

Start with a Virtual PLC

var memory = new MewtocolSlaveMemory();
memory.DataRegisterWords[100] = 253;
memory.InternalRelayWords[10] = 0x0001;

await using var app = ZeusHost.Create(builder =>
{
    builder.AddAcquisition(TimeSpan.FromMilliseconds(100));
    builder.AddVirtualChannel("mewtocol", new MewtocolSlaveResponder(stationNumber: 1, memory));
    builder.AddPanasonicMewtocol("plc", "mewtocol", new MewtocolOptions
    {
        StationNumber = 1
    }, points: map => map
        .DtWord("temperature", address: 100, scale: 0.1).Writable("temperature")
        .RBit("running", wordAddress: 10, bitOffset: 0).Writable("running"));
});

await app.StartAsync();
var temperature = app.Points.Get<double>("temperature");
await app.Points.WriteAsync("temperature", 18.6);

Code	Meaning
MewtocolSlaveMemory	Virtual PLC image for DT/LD/FL registers and X/Y/R/L contact words
MewtocolSlaveResponder(1, memory)	Simulates station 01
StationNumber = 1	Two-digit station number in the MEWTOCOL frame
.DtWord(..., 0.1)	DT100 raw word is scaled by 0.1; write-back reverses the scale

Run sample: samples/Zeus.Samples.Console.Mewtocol.

Connect to a Real PLC

MEWTOCOL-COM is commonly used over serial or RS-485. Serial settings come from the PLC project:

await using var app = ZeusHost.Create(builder =>
{
    builder.AddSerialPort("mewtocol", "COM3", 9600);
    builder.AddPanasonicMewtocol("plc", "mewtocol", new MewtocolOptions
    {
        StationNumber = 1
    });
});

If the site uses an Ethernet-to-serial gateway or TCP tunnel, use a TCP channel:

builder.AddTcpClient("mewtocol", "192.168.250.1", 9094);
builder.AddPanasonicMewtocol("plc", "mewtocol", new MewtocolOptions { StationNumber = 1 });

Read/Write API

var plc = app.Devices.Get<MewtocolDevice>("plc");

var dt = await plc.ReadDataRegistersAsync(100, 2);
await plc.WriteDataRegistersAsync(110, [10, 20, 30]);

var relays = await plc.ReadInternalRelayWordsAsync(10, 1);
await plc.WriteInternalRelayWordsAsync(10, [0x0001]);

Raw MEWTOCOL commands are also available:

string data = await plc.ExecuteAsync("RD", "D0010000101");

Memory Areas

Area	Commands	Point helpers
DT data registers	RD / WD	.DtWord(...) / .DtBit(...)
LD link data registers	RD / WD	.LdWord(...)
FL file registers	RD / WD	.FlWord(...)
X external input words	RC	.XWord(...) / .XBit(...)
Y external output words	RC / WC	.YWord(...) / .YBit(...)
R internal relay words	RC / WC	.RWord(...) / .RBit(...)
L link relay words	RC / WC	.LWord(...) / .LBit(...)

Bit points are written by reading the owning word, changing only the target bit, then writing the word back. X inputs are driven by the PLC, so JSON and the point map reject writable X points.

Points

builder.AddPanasonicMewtocol("plc", "mewtocol", new MewtocolOptions
{
    StationNumber = 1,
    WordOrder = MewtocolWordOrder.HighWordFirst
}, points: map => map
    .DtWord("temperature", 100, 0.1).Writable("temperature")
    .Int16("pressure", MewtocolDataArea.DataRegister, 120)
    .Real("flow", MewtocolDataArea.DataRegister, 130)
    .RBit("running", 10, 0).Writable("running"));

MEWTOCOL raw words are 16-bit. UInt32, Int32, and Real occupy two consecutive words; MewtocolOptions.WordOrder controls word order and defaults to high word first.

JSON Configuration

{
  "channels": [
    {
      "name": "mewtocol",
      "type": "serial",
      "options": {
        "portName": "COM3",
        "baudRate": 9600
      }
    }
  ],
  "devices": [
    {
      "name": "plc",
      "channel": "mewtocol",
      "type": "panasonic-mewtocol",
      "options": {
        "unitId": 1
      },
      "points": [
        {
          "name": "temperature",
          "options": {
            "area": "dt",
            "address": 100,
            "dataType": "word",
            "scale": 0.1,
            "writable": true
          }
        },
        {
          "name": "running",
          "options": {
            "area": "r",
            "address": 10,
            "bit": 0,
            "dataType": "bit",
            "writable": true
          }
        }
      ]
    }
  ]
}

Virtual MEWTOCOL PLC:

{
  "name": "mewtocol",
  "type": "virtual",
  "options": {
    "responder": "mewtocol",
    "unitId": 1
  }
}

A ready-to-copy serial sample is at samples/Zeus.Samples.Console.Config/zeus-mewtocol.json.

Common Issues

Symptom	Likely cause	Fix
Timeout	Station number, serial parameters, or TCP tunnel port is wrong	Test with MewtocolSlaveResponder, then check PLC settings
BCC failure	Baud/parity mismatch or the peer is not MEWTOCOL-COM ASCII	Verify serial settings and protocol mode
Error code returned	Memory area, address, or count unsupported	Inspect the MEWTOCOL error code and PLC manual
32-bit word order is wrong	PLC project uses opposite word order	Change MewtocolOptions.WordOrder
Write-back did not run	Point is not writable, or the point is an X input	Mark the point writable; X inputs cannot be written

Next: Points and Acquisition.