6 DATA COMMUNICATION USING THE NON PROCEDURE PROTOCOL
6.3 Data Communications Precautions
The following describes the precautions to be taken during non procedure protocol data communications.
(1) The Q series C24 transmission sequence initialization conditions
The initial status indicates the status where transmission has stopped and reception data has been discarded.
The Q series C24 transmission sequence initialization conditions are as follows.
1)When the power is turned on, the Reset switch on the CPU panel is operated, or the Q series C24 mode is switched
2)When the receive data was cleared.
3)When the CD signal was turned off when data communications were performed by setting CD terminal check enable during
(2)Generation of framing error in external device
When nothing is transmitted from the Q series C24 to the external device through the
Send an arbitrary code to identify the head of the send data from the Q series C24 to the external device.
Before data communication check the Q series C24 interface specifications.
(3)Data communications with external device (computer, etc.) over a multidrop link
When the external device PLC CPU are connected by a 1:n multidrop link, each the Q series C24 receives the data transmitted by the external device.
With a multidrop link, receive data by user frame (
1).
If data is not received by user frame, a sequence program that ignores the receive data other than the receive data addressed to the local station by sequence program, including the data indicating the objective PLC CPU in the message, must be written.
(Sample message)
(Example) |
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STX |
| Space |
| Station |
| Station |
| Data length |
| CR |
| LF |
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| No. 0 |
| No. 2 |
| Data |
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| (BIN data) |
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(02H) |
| (20H) |
| (32H) |
| (32H) |
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| (0DH) |
| (0AH) |
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1 See chapter 11 of User's Manual (Application)
6 - 30 | 6 - 30 |