4 SETTINGS AND PROCEDURES PRIOR TO OPERATION
In linked operation, all data received from one of the two interfaces is transmitted from the other interface. In this case, exclusive control of the received data is necessary when data is communicated using the nonprocedure protocol since all the connected stations receive the data. When data communication is performed using the MC protocol, only the Q series C24 having the station number designated in the message performs the process designated by the command. Furthermore, when data communication is performed using QnA compatible 2C/3C/4C frames of the MC protocol, the header information for linked operation is added to messages directed to other stations linked by multidrop connection.
Processing performed by the Q series C24 connected to an external device
•The header information is added to the command messages received from the external device that are directed to other stations and sends them to the stations through the other interface.
•The header information is deleted from the response messages received from other stations and sends them to the external device using the other interface.
(The header information is also sent during m:n connection.)
bOperation of the accessed station
The accessed station processes the request contained in the command message, adds the header information to a response message, and sends it using the interface that received the command message.
REMARK
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The following describes the header information that is added by the Q series C24 to a message in linked operation.
1)When communicating with ASCII code (formats 1 to 4)
The following 13/15 character header information is added immediately before the control code (ENQ/STX/ACK/NAK) at the start of each message (13 characters for formats 1, 3 and 4; 15 characters for format 2).
2)When communicating in binary mode (format 5)
The following 10 byte header information is added immediately before the control code (DLE + STX) at the start of each message.
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| (In ASCII code communication) |
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| "STX" in format 3 |
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| (In binary code communication) |
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| Existence in format 2 |
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| FramelinkforNo.ID | StationNo. |
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| stationModuleNo. stationlinkfor | dataSystem |
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No.Block | linkforNo.IDFrame |
| No.Station |
| forNo.I/OModule stationlink | No.stationModule stationlinkfor |
| dataSystem | E | No.Block | No.IDFrame |
| D | S | dataSystem | forNo.I/OModule stationlink | D | S | bytesdataofNo. |
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H | L | H | L | H | L | H | - | - | L | H | L | H | L |
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Header information (13/15 characters) |
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| Header information (10 byte) |
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4 - 19 | 4 - 19 |