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FUNCTION CODE 02 – READ INPUT STATUS FU NCT IO N CO DES
40 1TG C908004M0 201
Function codes and their relevant address range are shown in the table below.
Function Codes Address / Mapping Area Starting Address used in Modbus
Frame
FC02 10001-19999 0-9999
FC04 30001-39999 0-9999
FC03, 06, 16 40001-49999 0-9999
Table 15 Address ranges of Function Codes
8.2. Function Code 02 – Read Input Status
This function allows the control system to obtain the ON/OFF status of discrete inputs from
the MNS Digital Gateway. With function code 2 following information can be requested.
• Life Bits
• Status Information
• Control Access Information
• Alarms
• Trips
The valid address range: 10001-19999.
8.3. Function Code 03 – Read Holding Registers
With function code 03, the control system can read the registers that can store the numerical
data, which can be driven to external devices as mentioned below.
• Measuring Values
• Status as Word-oriented bits
• Alarm structure (Warnings/Trips)
The valid address range: 40001-49999
8.4. Function Code 04 – Read Input Registers
Function code 04 obtains the contents of the input registers. These locations receive their
values from devices connected to the I/O structure of field units and can only be referenced,
not altered within the system or via MODBUS as mentioned below.
• Status as Word-oriented bits
• Alarm structure (Warnings/Trips)
The valid address range: 30001-39999