Mitsubishi MELSEC LJ71C24, Руководство пользователя

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15 - 10 15 - 10
15 TROUBLESHOOTING
15.1.4 Reading the data communication status (Transmission sequence status)
This section explains how to read the current status of the data communication using
the MC protocol stored in the buffer memory.
When using GX Works2, check in the "Intelligent Function Module Monitor" screen.
(Refer to the GX Works2 Version1 Operating Manual (Intelligent Function Module).)
When a transmission problem occurs, read operation is executed to check the status
of the data communication using the MC protocol.
(1) Transmission sequence status (address: 255
H
/265
H
)
The status of data communication using the MC protocol is stored as a numeric
value as shown below.
b15
to
b0
0 to 9
0 to 9
Buffer memory address
265
H
(Information on the CH1 side)
(Information on the CH2 side)
255
H
The following shows the correspondence between the numerical values in the
transmission sequence status storage area and the data communication status.
"6" "1"..."6" is repeated afterward.
Values 7 to 9 are stored when "mode switching" or "initialization
of transmission sequence" is performed.
E
N
Q
S
ta
tion
nu
m
ber
H
L
Request
to CPU
Response
from
CPU
ACK
or
NAK
Message wait
Request from an external device
External
device
C24
Stored
value
1 0 3 4 5 6
2
REMARKS
When the target interface is not set to use the MC protocol, "0" is stored in the
transmission sequence status (address: 255
H
/265
H
).
(2) Example of a program that reads from transmission sequence
status (address: 255
H
/265
H
)
The following shows an example of a program that reads from the transmission
sequence status.
(input/output signals X/Y00 to X/Y1F of the C24)
Example of FROM instruction
b15 to b0
0
4
D0
D1
The CH1 side is waiting to receive a command message.
CH2 is accessing the programmable controller
CPU upon reception of a command message.
Reads the status of data communication
on the CH1 side from address 255
H
.
Reads the status of data communication
on the CH2 side from address 265
H
.
Read command