Omron Host Link

The Host Link module targets Omron PLC ASCII Host Link communication. It supports @UU station frames, FCS checks, CIO/LR/HR/AR/DM word access, point acquisition, write-back by point name, and virtual PLC simulation.

Start with a Virtual PLC

var memory = new HostLinkSlaveMemory();
memory.DataMemoryWords[100] = 253;
memory.CioWords[10] = 0x0001;

await using var app = ZeusHost.Create(builder =>
{
    builder.AddAcquisition(TimeSpan.FromMilliseconds(100));
    builder.AddVirtualChannel("host-link", new HostLinkSlaveResponder(unitNumber: 0, memory));
    builder.AddOmronHostLink("plc", "host-link", new HostLinkOptions
    {
        UnitNumber = 0
    }, points: map => map
        .DmWord("temperature", address: 100, scale: 0.1).Writable("temperature")
        .CioBit("running", address: 10, bitOffset: 0).Writable("running"));
});

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

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

Connect to a Real PLC

Serial settings depend on the PLC project:

await using var app = ZeusHost.Create(builder =>
{
    builder.AddSerialPort("host-link", "COM3", 9600);
    builder.AddOmronHostLink("plc", "host-link", new HostLinkOptions
    {
        UnitNumber = 0
    });
});

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

builder.AddTcpClient("host-link", "192.168.250.1", 9600);
builder.AddOmronHostLink("plc", "host-link", new HostLinkOptions { UnitNumber = 0 });

Read/Write API

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

var dm = await plc.ReadDataMemoryWordsAsync(100, 2);
await plc.WriteDataMemoryWordsAsync(110, [10, 20, 30]);

var cio = await plc.ReadCioWordsAsync(10, 1);
await plc.WriteCioWordsAsync(10, [0x0001]);

Raw Host Link commands are also available:

string data = await plc.ExecuteAsync("RD", "01000002");

Memory Areas

Area	Read command	Write command	Point helpers
CIO / IR	RR	WR	.CioWord(...) / .CioBit(...)
LR	RL	WL	.LinkWord(...) / .LinkBit(...)
HR	RH	WH	.HoldingWord(...) / .HoldingBit(...)
AR	RJ	WJ	.AuxiliaryWord(...) / .AuxiliaryBit(...)
DM	RD	WD	.DmWord(...) / .DmBit(...)

Bit points are written by reading the owning word, changing only the target bit, then writing the word back.

Points

builder.AddOmronHostLink("plc", "host-link", new HostLinkOptions
{
    UnitNumber = 0,
    WordOrder = HostLinkWordOrder.HighWordFirst
}, points: map => map
    .DmWord("temperature", 100, 0.1).Writable("temperature")
    .Int16("pressure", HostLinkArea.DataMemory, 120)
    .Real("flow", HostLinkArea.DataMemory, 130)
    .CioBit("running", 10, 0).Writable("running"));

Host Link raw words are 16-bit. UInt32, Int32, and Real occupy two consecutive words; HostLinkOptions.WordOrder controls word order.

JSON Configuration

{
  "channels": [
    {
      "name": "host-link",
      "type": "serial",
      "options": {
        "portName": "COM3",
        "baudRate": 9600
      }
    }
  ],
  "devices": [
    {
      "name": "plc",
      "channel": "host-link",
      "type": "omron-host-link",
      "options": {
        "unitId": 0
      },
      "points": [
        {
          "name": "temperature",
          "options": {
            "area": "dm",
            "address": 100,
            "dataType": "word",
            "scale": 0.1,
            "writable": true
          }
        },
        {
          "name": "running",
          "options": {
            "area": "cio",
            "address": 10,
            "bit": 0,
            "dataType": "bit",
            "writable": true
          }
        }
      ]
    }
  ]
}

Virtual Host Link PLC:

{
  "name": "host-link",
  "type": "virtual",
  "options": {
    "responder": "host-link",
    "unitId": 0
  }
}

Common Issues

Symptom	Likely cause	Fix
Timeout	Unit number, serial parameters, or TCP tunnel port is wrong	Test with HostLinkSlaveResponder, then check PLC settings
FCS failure	Baud/parity mismatch or the peer is not Host Link ASCII	Verify serial settings and protocol mode
End code returned	Memory area, address, or count unsupported	Inspect HostLinkException.EndCode and PLC manual
32-bit word order is wrong	PLC project uses opposite word order	Change HostLinkOptions.WordOrder

Next: Points and Acquisition.