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The Mitsubishi MELSEC protocol is used for communication with Mitsubishi PLCs (MELSEC L-series and , MELSEC Q-series series, and MELSEC iFX-series) equipped with Ethernet communication modules. The UDP variant using the UDP protocol (on the the TCP/IP-UDP line) and the TCP variant using the TCP protocol (on the TCP/IP-TCP line) are implemented. Read and write commands are supported.
Following The following rame formats are supported (see see Frame type protocol parameter): 1E, 3E, 4E. Both binary and ASCII message encoding are supported (see the Code type protocol parameter). ASCII-encoded messages are approximately 2 times longer than binary-encoded messages.
Reading and writing various types of objects (device codes) is supported. These objects are bit-oriented or word-oriented, and the interpretation of several (16 or 32) consecutive bit objects as a signed/unsigned number or two consecutive word objects as a number (unsigned, signed, a real 32-bit number) is supported. Access to a specific bit of a word object is also supported.
Communication was tested against the Mitsubishi FX5UC-32MT/DSS-T model (frame 3E, binary encoding, TCP communication).
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- Communication line category: TCP/IP-UDP (UDP variant) or TCP/IP-TCP (TCP variant).
- TCP/IP-UDP parameters:
- Host: IP address or of the network interface that is used for communication by the KOM process. A symbolic name that can be translated to an IP address can be entered too.
Note: a symbolic name ALL or * can be entered - in which case all available interfaces are used. - Port: UDP port number that is used for communication by the KOM process.
- Note: The parameters of the backup server (Host and Port) are not used in this protocol.
- Host: IP address or of the network interface that is used for communication by the KOM process. A symbolic name that can be translated to an IP address can be entered too.
- TCP/IP-TCP parameters:
- As the Host, Port, and Line Number parameters are not used (the PLC address is configured on the station), arbitrary values can be specified.
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| Parameter | Meaning | Unit | Default value | ||||||
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| General Parameters | |||||||||
| Type of message encoding:
| - | Binary code | ||||||
| The type of frame (header) used. This type must be the same as the type configured on the Mitsubishi PLC side
| - | 3E | ||||||
| 1E/3E/4E Frames Common Parameters | |||||||||
| Hexadecimal number (00-FF) specifying the station network module number (for remote stations). Keep the default value FF for directly connected PLCs. | - | FF | ||||||
| Specification of the time to wait for a response in 250 ms units, which is sent in the message header (a value of 0 means waiting without restriction). The default value of 16 means waiting for 4 seconds. | 250 ms | 16 | ||||||
| The maximum number of objects read in one message. The range is 1-960. Objects can be of bit or word type. A bit object is transmitted as 1 bit (2 bits in ASCII encoding), a word object is transmitted as 2 bytes (4 bytes in ASCII encoding). | - | 480 | ||||||
| Maximum response size - the size of the pure data. The range is 2-8192 bytes. | byte | 512 | ||||||
| 3E/4E Access Route Parameters | |||||||||
| Destination network number (for multidrop systems/stations on remote networks). The value is entered in decimal and is in the range 0-255. When communicating with a directly connected station, the value 0 is entered. Other values (see documentation) are entered when communicating with stations located on other network segments (it can also be serial lines) located behind the directly connected station. See Literature for more information. | - | 0 | ||||||
| Target I / O module number (for multidrop/multiCPU/redundant systems). The value is entered in hexadecimal and is in the range 0000-FFFF. When communicating with a directly connected station, the value 03FF is entered. Other values (see documentation) are entered when communicating with stations located on other network segments (it can also be serial lines) located behind a directly connected station, in the case of multidrop connections, and in the case of working with redundant PLCs and PLCs with multiple CPUs. See Literature for more information. | - | 03FF | ||||||
| Destination station number (for multidrop/multiCPU/redundant systems). The value is entered in hexadecimal and is in the range 00-FF. When communicating with a directly connected station, the value 00 is entered. Other values (see documentation) are entered in the case of a multidrop connection. See Literature for more information. | - | 00 | ||||||
| Other Parameters | |||||||||
| Maximum count of request retries. If no response returns after a request had has been sent, the station's status will change to a communication error. | - | 2 | ||||||
| Timeout before resending a request if no response has been received. | s | 0.1 | ||||||
| Timeout for receiving a response. The value of the parameter should be greater than the time corresponding to the value of the Monitoring Timer parameter. | s | 1.0 | ||||||
| Logging of detailed debug information about communication in the line log. | YES/NO | NO | ||||||
| Text reports of messages. If Code type=ASCII code, message listings will be in text form. | YES/NO | NO | ||||||
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| Device type | Device code | Data type |
|---|---|---|
| Special relay | SM | bit |
| Special register | SD | word |
| Input | X | bit |
| Output | Y | bit |
| Internal relay | M | bit |
| Latch relay | L | bit |
| Annunciator | F | bit |
| Edge relay | V | bit |
| Link relay | B | bit |
| Data register | D | word |
| Link register | W | word |
| Timer Contact | TS | bit |
| Timer Coil | TC | bit |
| Timer Current value | TN | word |
| Retentive Timer Contact | STS | bit |
| Retentive Timer Coil | STC | bit |
| Retentive Timer Current value | STN | word |
| Counter Contact | CS | bit |
| Counter Coil | CC | bit |
| Counter Current value | CN | word |
| Link special relay | SB | bit |
| Link special register | SW | bitword |
| Direct access input | DX | bit |
| Direct access output | DY | bit |
| Index register | Z | word |
| File register | R | word |
Device numberKotva device_number device_number
For a specific type of device (device code), individual objects are identified by a number (device number). When using 3E and 4E frames, a 3-byte number is specified, when using a 1E frame, a 4-byte number is specified. Numbering starts from 0, the maximum number for a specific device type depends on the specific PLC.
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Note: when interpreting 32-bit numbers, the data is interpreted as little-endian (a lower word at a lower address, higher at a higher address).
ItemsKotva items items
The number of elements for structured I/O tags with configured Destination column. Every read element (1,2,3 .. items) will be written to one item of the destination column.
Note: All "items" elements are read at once. If e.g. 100 elements of device type (device code) which has data of word type (e.g. address D10, WORD, 100), are configured, it means reading of a block of 200 bytes. If the number of objects is greater than the value of the Max Points, parameter, or the data size is greater than the Max Data Bytes, the reading will not be performed and an error message Too many elements in point < I/O tag name> will be added to the line log.
Configuration examples:
- X10 - Input 10, interpreted as a BIT (default)
- D0 - Data register 0, interpreted as a WORD (default)
- M12, WORD - Internal relays 12-27, interpreted as a WORD
- D4, REAL - Data registers 4 and 5, interpreted as REAL
- Y10, BIT, 20 20 - Inputs 10-29, interpreted as BIT (default), assigned to 20 items of the Destination column
- D4, REAL, 10 - Data Data registers 4-23, each couple interpreted as REAL, assigned assigned to 10 items of the the Destination column
- D4, WORD, 10 - Data register 4-13, interpreted as WORD, assigned to 10 items of the Destination column
- R1000, , 3 - File registers 1000-1003, interpreted as WORD (default), assigned to 3 items of the Destination column
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- Ver. 1.0 – March 10, 2021 - a document created
- Ver. 1.1 – October 24, 2023 - support for file registers
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