The specific steps for displaying negative values are as follows:

1. Establish the variable "z32", with the data type of unsigned 32-bit value and the address of modbus register address: 3x40000 1.

2.485 communication equipment directly reads its data with wincc, and a ModbusTCP/ModbusRTU converter needs to be added in the middle to convert ModbusRTU protocol into ModbusTCP protocol and communicate with host computer WinCC through Ethernet.

3. Establish the internal variable "b_float" whose data type is 32-bit floating point number IEEE 754.

4. Then set up a test screen, add an IO field, and then enable C operation.

5. Through the Modbus polling debugging software test, the data type is displayed in Float CD AB format.

6. After the above steps are completed, wincc's 32-bit floating-point number can display negative values.