Data Designation Items For Qna Compatible 3C/4C Frames - Mitsubishi MELSEC Q Series Reference Manual

3.1.6 Data designation items for QnA compatible 3C/4C frames

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3 WHEN COMMUNICATING USING THE QnA COMPATIBLE 3E/3C/4C FRAMES OR 4E FRAME
This section explains common data items in each message and how to specify them
when data communication is performed using QnA compatible 3C/4C frames for the
C24.
(1) Control codes
The following shows the codes and contents of the data (message head data,
etc.) that have special meanings for the C24 transmission control in each control
procedure.
The control codes used by each ASCII mode frame are indicated by an
in the ASCII code column in the table.
The control codes used by the binary mode QnA compatible 4C frames are
indicated by an
The control codes are used in the same way in each message.
Symbol Code
Description
name (hexadecimal)
NUL 00
H
STX 02 Start of Text
H
ETX 03 End of Text
H
EOT 04 End of Transmission
H
ENQ 05
H
ACK 06 Acknowledge
H
LF 0A
H
– –
POINT
When the fields "Number of data bytes" to "Data area" in a message include "10
the "10 " DLE code (expressed as additional code in the document) is added
H
immediately before the data, after which the data communication is performed (as
"10 " "10 " + "10
H H H
binary code using QnA 4C frame format 5.
The C24 adds the response message.
An example of the message structure is shown in Section 3.1.7 (2).
(a) Null codes (00
are Null codes in a message, they are not processed.
(b) EOT and CL are codes for initializing the transmission sequence for data
communications in ASCII code using the MC protocol and for placing the
C24 in wait status to receive commands from an external device.
According to the format used, EOT or CL is sent to the C24 when giving the
following commands from the external device side.
1) Cancel a read/write request issued by the immediately preceding
command. (When a write request was issued, and data was already
written to the programmable controller CPU, the write request cannot
be canceled.)
2) Before commands are sent, place the C24 in the command receive
wait status.
3) If data communications cannot be carried out normally, place the C24
in the same status as when it was started up.
mark in the binary code column in the table.
ASCII Binary
code code
Null
Enquiry
Line Feed
–
"). This is valid when data communication is performed in
) are ignored in all messages. That means that even if there
H
Symbol Code
Description
name (hexadecimal)
CL 0C
H
CR 0D Carriage Return
H
DLE 10 Data Link Escape
H
Negative
NAK 15
H
Acknowledge
F6 (For system)
QnA
H
compati (QnA compatible 4C
F8
H
ble frame ID code)
frame
(QnA compatible 3C
F9
H
ID
frame ID code)
number
FA (For system)
H
mark
ASCII Binary
code code
Clear
",
H
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