GNM3D Series and GNM3T Series COMMUNICATION PROTOCOL Version 1 Revision 1
Index 1.1 1.2 Introduction ........................................................................................................................................... 3 MODBUS functions ............................................................................................................................... 3 1.2.1 1.2.2 1.2.3 1.2.4 1.2.5 1.3 Application notes ................................................................................................................................... 6 1.3.
1.1 Introduction The RS485 serial interface supports the MODBUS/JBUS (RTU) protocol. In this document only the information necessary to read/write from/to GNM3D and GNM3T series has been reported (not all the parts of the protocol have been implemented). For a complete description of the MODBUS protocol please refer to the latest revision of the “Modbus_Application_Protocol” document that is downloadable from the www.modbus.org web site. 1.
Response frame (incorrect action) Description Physical address Function code Exception code CRC Length 1 byte 1 byte 1 byte 2 bytes Value 1 to F7h (1 to 247) 83h 01h, 02h, 03h, 04h (see note) Note Possible exception : 01h: illegal function 02h: illegal data address 03h: illegal data value 04h: slave device failure 1.2.2 Function 04h (Read Input Registers) This function code is used to read the contents of a contiguous block of input registers (word).
Response frame (incorrect action) Description Length Value Physical address 1 byte 1 to F7h (1 to 247) Function code 1 byte 86h Exception code 1 byte 01h, 02h, 03h, 04h CRC 2 bytes Note Possible exception : 01h: illegal function 02h: illegal data address 03h: illegal data value 04h: slave device failure 1.2.
1.3 1.3.1 Application notes RS485 general considerations 1. To avoid errors due to the signal reflections or line coupling, it is necessary to terminate the bus at the beginning (master side, if not already embedded, by inserting a 120 ohm 1/2W 5% resistor between line B and A) and at the end (in GNM3D and GNM3T series interface by connecting the terminal A-with the terminal T in the last instrument. 2.
2 TABLES 2.1 Data format representation The variables are represented by integers or floating numbers, with 2’s complement notation in case of “signed” format, using the following: Format INT16 UINT16 INT32 UINT32 UINT64 IEEE754 SP IEC data type INT UINT DINT UDINT ULINT Description Integer Unsigned integer Double integer Unsigned double integer Unsigned long integer Single-precision floating-point Bits 16 16 32 32 64 32 Range -32768 .. 32767 0 .. 65535 -231 .. 231 0 .. 232-1 0 ..
Application Easy connection Mode Bidirectional Mode 2.
2.4 Instantaneous variables and meters (grouped by variable type) MODBUS: read only mode with functions code 03 and 04 VARIABLE ENG. UNIT Table 2.
Instantaneous variables and meters (grouped by phase) MODBUS: read only mode with functions code 03 and 04 Modicom address 300249 300255 Physical address 00F8h 00FEh Length (words) VARIABLE ENG. UNIT System variables Table 2.
2.5 Firmware version and revision code MODBUS: read only mode with functions code 03 and 04 limited to a word at a time Modicom address 300771 300772 2.6 Physical address 0302h 0303h Length (words) 1 1 VARIABLE ENG. UNIT Version code Revision code Data Format UINT 16 UINT 16 Table 2.6-1 Notes Value=1: Version “B” Modbus Value=0: Revision “0” etc. GARO identification code MODBUS: read only mode with functions code 03 and 04 limited to a word at a time Modicom address 300012 2.7 2.7.
address 2.7.5 address 1010h (words) 2 ENG. UNIT Integration time for dmd power calculation Format UINT 32 Value min = 1 Value max = 30 Other functions configuration menu MODBUS: read and write mode Modicom address 304353 Physical address 1100h Length (words) 1 304354 1101h 304355 Table 2.8-5 VARIABLE ENG.
308196 2003h 1 RS485 Stop bit UINT 16 308197 2004h 1 Max number of words readable with a single Modbus request UINT 16 Value 0 = 1 stop bit Value 1= 1 (default) Value 2 =2 (only if parity is even) Any other value = 1 stop bit Value = 50 (words) Note: The number of stop bits is fixed to “1” if parity is EVEN. 2.7.8 Reset commands MODBUS: read and write mode Modicom address 316385 Physical address 4000h Length (words) 1 316386 4001h 1 2.7.9 Table 2.8-8 VARIABLE ENG.
