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Modbus RTU, inputs (In-A, In-B) Cable connections Terminals Max cable size 1.5 mm² MULTICAL® 403 MULTICAL® 603 MULTICAL® 803 Pulse input Terminal 65: Pulse In A/In-A (+) Terminal 66: Pulse In A/In-A (-) Terminal 67: Pulse In B/In-B (+) Terminal 68: Pulse In B/In-B (-) Modbus Terminal 138: RS-485 B/+ Terminal 139: RS-485 GND Terminal 137: RS-485 A/- Pulse inputs The module is equipped with two pulse inputs, In-A and In-B, to collect and + accumulate pulses, e.g. from water and electricity meters. The pulse inputs are physically placed on the module. However, the accumulation and logging of values are performed by the MULTICAL® calculator. When installing a module with pulse inputs in slot 2 of MULTICAL® 603 and + MULTICAL® 803, the pulse inputs will be registered in the meter as In-A2 and In-B2. Data The communication is RS485 based. To ensure proper communication a twisted shielded pair cable is mandatory. The shield must be connected to the GND Terminal. All devices in the Modbus RTU system should be connected in a line topology. The communication line must be terminated with 120 Ohm resistors between the A and B leads, at both ends. 65 In-A 66 67 In-B 68 4 Kamstrup A/S • FILE100001610_B_EN-58101497_L1_06.2024
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Modbus RTU, inputs (In-A, In-B) Communication from module MULTICAL® 403 MULTICAL® 603 MULTICAL® 803 Protocol According to the Modbus over Serial Line, Specification and Implementation Guide V1.02. Modbus addressing The module may be addressed as a Modbus slave unit in the range from 1-247. By default, the Modbus address equals the last three digits of the meter’s customer number. If the customer number of the meter results in an address larger than 247, only the last two digits are used for the Modbus address of the module. Note : If the customer number of the meter ends with 000, the Modbus module automatically changes to address 247. Note : The Modbus Slave ID or Bus Address is configured and stored in the MULTICAL®. Communication speed The module supports baud rates from 300 to 115200 baud. The parity and stop bits are to be selected as one of the following: no parity 1 stop, no parity 2 stop, even parity 1 stop or odd parity 1 stop. Supported Modbus function codes The module supports a subset of Modbus function codes for reading and writing. Generally, function codes and addresses are written in hexadecimal format shown by the prefix 0x. Supported function codes and their possible exception codes: • 0x03 Read Holding Registers with exception codes: • 0x02 – Illegal data address • 0x03 – Illegal data value • 0x04 Read Input Registers with exception codes: • 0x02 – Illegal data address • 0x03 – Illegal data value • 0x08 Diagnostics with exception code: • 0x01 – Illegal function • Subcode 0x01 Restart with exception code: • 0x03 – Illegal data value • 0x10 Write Multiple registers with exception code: • 0x02 – data address • 0x03 – Illegal data value • 0x2B Encapsulated interface transport with exception code: • 0x01 – Illegal function • Subcode 0x0E Read Device Identification with exception code: • 0x03 – Illegal data value • 0x41 and 0x42 Reserved as Kamstrup Specific Function code Kamstrup A/S • FILE100001610_B_EN-58101497_L1_06.2024 5
