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CHAPTER 12 COMMUNICATIONS USING A FIXED BUFFER
12
12.6 Data Format
12.6.2 Application data
(e) End codes
An error code is stored in the end code added to a response. For the error codes, refer to the error code list.
( Page 268, Section 16.7.1) End codes are stored in the complete status area (in the control data) of the
BUFSND and BUFRCV instructions, as well as the communication status storage area of the buffer memory.
If an error code related to MC protocol communications or communications using a random access buffer is stored during
communications using a fixed buffer, it may be caused by the following.
Depending on the restrictions of the buffers of the own station and destination station, data may be divided for
communications. Data received separately is restored (reassembled) by the E71 for communications. The received data is
restored (reassembled) based on the data length in the communication data. The E71 performs the following processes if
data in the communication data is incorrect.
● If the data length specified immediately after the subheader is smaller than the amount of text data received
1) The data immediately after the text data equivalent to the data length specified immediately after the subheader is
regarded as the next message.
2) Because the header of each message is a subheader, an E71 processes data according to the code in the subheader.
3) If the subheader contains a code that is not recognized by an E71, the E71 sends a response notifying about an
abnormal end to the connected device.
In the figure above, the E71 returns a response containing a code obtained by changing the most significant bit of the
code processed as a subheader to 1.
For example, if the subheader of a command is 65
H
, the subheader of the response is E5
H
.
● If the data length specified immediately after the subheader is larger than the amount of text data received
• Sends the ABORT (RST) instruction to the connected device and closes the line.
• Notifies the CPU module that an open error has occurred by turning on Open abnormal detection signal (X18)
• Stores the error code in the open error code storage area. (The error code is not stored in the error log area.)
Cause Action
The data length value specified in the application data of the
message sent from a connected device to the E71 is different
from the actual text data size.
Specify the actual text data size for the data length in the
application data.
(Refer to "Remark" in this page.)
The subheader of the message sent from a connected
device to the E71 is incorrect.
Correct the subheader specified in the application data.
1) The E71 waits for the remaining data.
2) When the remaining data is received within the response monitoring timer value, the E71 processes data according
to the code in the subheader.
3)
If the remaining data could not be received within the response monitoring timer value, the E71 performs the
following processes.
Subheader Subheader
(2nd data)(1st data)
Data processed by the E71Data sent from the connected device
This section is processed
as a subheader.
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