Understanding Transmission Data In The Character Areas - Mitsubishi MELSEC Q Series Reference Manual

5.1.4 Understanding transmission data in the character areas

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(10) Sum check code
The sum check code is obtained by converting the lower byte (8 bits) of the
binary sum of the target data of the sum check into a 2-digit ASCII code
(hexadecimal).
When "sum check code: none" is set using the programming tool, the C24 does
not attach the sum check code to the transmission message. Also, the C24
processes data received as if it does not contain a sum check code.
When "sum check code: exist" is set, the C24 attaches the sum check code to
the transmission message. The C24 also checks the sum check code in the
received data.
The example below shows the contents of the sum check code.
(Example)
The following sum check code value is generated when character area
"M0000" is transmitted in format 1, with station number 0, PC number FF,
command BR (device memory batch read), and message wait 30 ms.
External device
side
Programmable controller
CPU side
(11) Error code
• An error code shows an error description when an abnormal response is
returned.
• Error codes are transmitted in 2-digit ASCII code (hexadecimal) in the range
from 00 to FF
H
• If multiple errors are generated at the same time, the C24 sends the error code
that is detected first.
• For more details on the error codes, refer to the User's Manual (Basic).
The transmission data that is handled in the character areas during data
communication between an external device and the programmable controller CPU
using various commands is the same as that when communicating using the QnA
compatible 3C/4C frames.
Refer to Section 3.1.7 for more details on the bit device data and word device data for
the transmission data contained in the character areas.
5 WHEN COMMUNICATING USING THE A COMPATIBLE 1C FRAMES
E
Station No. PC No. Command
N
Q
0 0 F F B R
05 30 30 46 46 42 52
H H H H H H
Sum check is performed within this range.
30 +30 +46 +46 +42 +52 +33
H H H H H H
=2C0
H
.
H
Character area Sum
Message
check
wait
code
3
M 0 0 0 0 C
33 4D 30 30 30 30 43 30
H H H H H H H H
+4D +30 +30 +30 +30
H H H H H H
0
H
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