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MELSEC-QnA Series Ethernet Parameter |
When MELSEC-QnA series Ethernet is used, it explains the method of setting the Ethernet parameter needed on the PLC side.
It is necessary to mount the setting concerning the port by the ladder program though the MELSEC-QnA series can do only the IP address setting by setting the parameter of GX Developer.
This sample project can be downloaded here.
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Hardware Setting |
The communication condition setting switch in front of the unit is set as follows.

* Switch numbers in parentheses indicate switch numbers for discontinued A1SJ71E71-B2/B5-S3.
* Use data code setting (SW2) in binary code (OFF).
* Use CPU communication timing (SW7) with "allow writing from other node when PLC is running" (ON).
* Units without a DIP switch on the front panel (such as A1SJ71E71N-T) have the DIP switch on the board.
* For more details, please refer to the Ethernet Unit manual.
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Network Parameters |
You can configure the IP address for QnA Series from the "Network Parameters" page of GX-Developer. When you use Automatic port (default 5000), you can configure the communication without a program. Describe the initial process and port control process in a ladder program when you wish to use anything other than automatic open UDP port (default 5000).

Open GX Developer's "Network Param" page, specify "Ethernet" for "Network Type," and enter the network number, group number, and station number.
When AJ71QE71 is installed in slot 0 (side of CPU), head I/O No:"0" and network No are set, and "1" and group No are set in "0" and the exchange number is set to "1". |
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Sample Confiugration |
When Ethernet is used by the MELSEC-QnA series, an initial processing program and the port processing of the Ethernet unit are needed.
The example of programming the sample when the Ethernet unit is installed in slot 0 is shown.
Please see the manual of PLC for the error processing of the Ethernet unit etc.
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Protocol |
Local Port |
Other IP Address |
Other Port |
| Connection1 |
UDP/IP |
1025 |
255.255.255.255 |
0xFFFF |
| Connection2 |
TCP/IP Unpassive |
1026 |
N/A |
N/A |
| Connection3 |
TCP/IP Fullpassive |
1027 |
192.168.0.1 |
1027 |
| IP Address |
192.168.0.2 |
| Existence Confirmation |
Sends ICMP packets three times every 2 seconds after 14 seconds. |
| Unit Address |
Ethernet unit is installed in I/O address 0. |
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Initial Program |

1. Set the local IP Address to "192.168.0.2."
2. Set Existence Confirmation Start Interval timer to 14 seconds (7*2 seconds).
3. Set Existence Confirmation Interval Timer to 2 seconds (1*2 seconds).
4. Set Communication Instruction during STOP to "enabled" (0xFFFF) for all connections.
5. Turn on Initial Request signal (Y19).
6. After Initial Complete signal (X19) turns on, set the TCP/IP port to wait OPEN.
* When IP address is set by the network parameter, the processing of (1) is unnecessary. |
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UDP/IP Open Processing |

1. Set Connection 1 protocol to UDP/IP (0x100).
2. Set Local Port # of Connection 1 to "1025".
3. Set Other IP Address to "0xFFFFFFFF" in order to enable broadcast communication.
4. Set Other Port # to "0xFFFF" in order to enable broadcast communication.
5. Turn ON Port OPEN Request (Y8).
- UDP/IP does not require connection processing. Y8 reset circuit is not required. Port remains open.
- If you do not specify the other PC, set Other IP Address to "0xFFFFFFFF" and Other Port # to "0xFFFF" in order to enable broadcast communication. |
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TCP/IP Unpassive Open Processing |

1. Set Connection 2 protocol to TCP/IP unpassive (0x8002).
2. Set "1026" to the local port of Connection 2.
3. Turn on Open Request (Y9) by default (this enables access from I/O Server).
4. When Open Complete signal (X11) turns off, turn Open Request off once and repeat step [3] again after 0.5 seconds.
- Configure Existence Confirmation properly when using TCP/IP.
- In order to return to wait OPEN state after the session is disconnected, make sure you wait a sufficient amount of time before attempting again. |
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TCP/IP Full Passive Open Processing |

1. Set Connection 3 protocol to TCP/IP full passive (0xC002).
2. Set "1027" to the local port of Connection 3.
3. Set "192.168.0.1" to Other IP of Connection 3.
4. Set "1027" to Other Port of Connection 3.
5. Turn on Open Request (Y9) by default (this enables access from I/O Server).
6. When Open Complete signal (X11) turns off, turn Open Request off once and repeat step [5] again after 0.5 seconds.
- Configure Existence Confirmation properly when using TCP/IP.
- In order to return to wait OPEN state after the session is disconnected, make sure you wait a sufficient amount of time before attempting.
- When using TCP/IP full passive communication, the port used by Windows will be locked after the session is closed. You may not be able to establish connection again for some time as a result. |
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