Add Modbus registers

This guide shows how to add registers to monitor in ModbusScope.

Before you start

You must have at least one connection and one device configured. See Configure a TCP connection or Configure an RTU connection.

Steps

  1. Click Register Settings in the toolbar.

    Register settings dialog

  2. Click Add to insert a new register row.

  3. In the Expression column, enter the register address using ${...} syntax (e.g. ${40001}). See Reference: Register syntax for all supported forms.

  4. In the Name column, enter a label for the graph legend.

  5. In the Color column, pick a line color.

  6. In the Data type column, select the type that matches your device (16b, s16b, 32b, s32b, f32b). For coils and discrete inputs, the type is ignored.

  7. In the Y-axis column, select Y1 or Y2.

  8. Repeat steps 2–7 for each register.

  9. Click OK.

Result: The registers appear in the main window. They will be polled when you click Start Logging.

Tips

  • To reference a specific device, add @DEVICE to the expression (e.g. ${40001@2} reads from device 2). Device 1 is used by default.

  • To calculate or combine values, use an expression instead of a bare address. See Write expressions.

  • Importing registers from a .mbc file is faster than adding them by hand. See Import from MBC file.

  • Consecutive register addresses are read in a single Modbus packet. Gaps between addresses split the request and slow down the poll rate. See Optimize poll rate.

See also