Mitsubishi MELSEC Q Series Reference Manual page 98

(3) Number of data bytes (for QnA compatible 4C frame format 5)
(4) Frame ID number
(5) Station number to self-station number
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3 WHEN COMMUNICATING USING THE QnA COMPATIBLE 3E/3C/4C FRAMES OR 4E FRAME
The number of data bytes is used to inform the external device of the total
number of bytes of data, excluding additional codes, between the frame ID
number and data section or the frame ID number and complete code (error code).
(Since the programmable controller CPU does not check the number of data
bytes in command messages received from an external device, it can also be
designated as dummy data 00
Number of data bytes is transmitted as a 2-byte value in ascending order, low
byte (L: bit 0 to 7) to high byte (H: bit 8 to 15).
(Example)
A response message after data was read from the programmable controller
CPU
L H
10 02 0F 00 F8 05
H H H
H H
The frame ID number is used to identify if the message to be communicated is a
QnA compatible 3C frame or a QnA compatible 4C frame.
The following shows the frame ID numbers that are designated during data
communications.
QnA compatible 3C frame
Communication in ASCII
code
QnA compatible 4C frame
Communication in binary
QnA compatible 4C frame
code
The values in the station number to local station number fields designate the
programmable controller station to be accessed by an external device. The four
sets of data identify the route until the access destination.
An example of designating the network number to request destination module
station number while accessing other stations is shown in Section 2.6.3.
• Station number
Station numbers are set to the C24 using the programming tool. They and
used to identify the C24 to which an external device accesses, or to identify the
C24 that is routed when accessing the programmable controller on another
station on CC-Link IE Controller Network, CC-Link IE Field Network,
MELSECNET/H, or MELSECNET/10.
, 00 .)
H H
L H
07 03 04 00 01
H H H H
H H
Specify the number of bytes in this range.(excluding additional codes)
Frame ID
Frame
Number.
"F9"
"F8"
F8
Data section
Data for the number
of designed device
points
L H L H
00 FF FF 00 00 01 10 10
H H
H H H H H
Note
Two characters, "F" and "9," are sent in that
order.
Two characters, "F" and "8," are sent in that
order.
One byte of F8
H
H L
10 10 10 03 33 41
H H H H H
H H
data is sent.
H
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