Mitsubishi Electric QJ71E71-100 User Manual page 158

Remark
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.
Data sent from the connected device
Subheader
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
is E5 .
H
● If the data length specified immediately after the subheader is larger than the amount of text data received
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.
• 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 storage
area.)
(2) No procedure
In the application data for communications in the "No Procedure" control method, the following data code is
expressed in a binary code. Communications are performed using a binary code regardless of the
communication data code setting.
In communications in the "No Procedure" control method, a subheader or data length setting is not added unlike the
"Procedure Exist" control method; therefore, all data are handled as a valid text. In addition, the E71 turns on Fixed buffer
reception status signal after storing the size of the received message (packet) in the data length storage area. It is
recommended to set a checking method. For example, include data length and a data type code in the application data of a
message so that the number of bytes and data type of the application data can be identified on the receiving side.
156
Data processed by the E71
(1st data)
Subheader
Text (command)
Maximum of 2046 bytes
(2nd data)
This section is processed
as a subheader.
, the subheader of the response
H