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21: D
ATA
L
INK
C
OMMUNICATION
21-6
O
PEN
N
ET
C
ONTROLLER
U
SER
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S
M
ANUAL
Special Internal Relays for Data Link Communication
Special internal relays M8005 through M8007 and M8140 through M8177 are assigned for the data link communication.
M8005 Data Link Communication Error
When an error occurs during communication in the data link system, M8005 turns on. The M8005 status is maintained
when the error is cleared and remains on until M8005 is reset using
WindLDR
or until the CPU is turned off. The cause of
the data link communication error can be checked using Online > Monitor, followed by Online > PLC Status > Error
Status: Details. See page 21-4.
M8006 Data Link Communication Prohibit Flag (Master Station)
When M8006 at the master station is turned on in the data link system, data link communication is stopped. When M8006
is turned off, data link communication resumes. The M8006 status is maintained when the CPU is turned off and remains
on until M8006 is reset using
WindLDR
.
When M8006 is on at the master station, M8007 is turned on at slave stations in the data link system.
M8007 Data Link Communication Initialize Flag (Master Station)
Data Link Communication Stop Flag (Slave Station)
M8007 has a different function at the master or slave station of the data link communication system.
Master station: Data link communication initialize flag
When M8007 at the master station is turned on during operation, the link configuration is checked to initialize the data link
system. When a slave station is powered up after the master station, turn M8007 on to initialize the data link system. After
a data link system setup is changed, M8007 must also be turned on to ensure correct communication.
Slave station: Data link communication stop flag
When a slave station does not receive communication data from the master station for 10 seconds or more in the data link
system, M8007 turns on. When a slave station does not receive data in 10 seconds after initializing the data link system,
M8007 also turns on at the slave station. When the slave station receives correct communication data, M8007 turns off.
M8140-M8176 Slave Station Communication Completion Relay for Separate Refresh Mode
Special internal relays M8140 through M8176 are used to indicate the completion of data refresh when the data link com-
munication is performed in the separate refresh mode. When data link communication with a slave station is complete, a
special internal relay assigned for the slave station is turned on for one scan time at both the master and slave station.
M8177 All Slave Station Communication Completion Relay
When data link communication with all slave stations is complete in either separate or simultaneous refresh mode, special
internal relay M8177 at the master station is turned on for one scan time. M8177 at slave stations does not go on.
Special Internal Relay
Slave Station Number
Special Internal Relay
Slave Station Number
M8140
Slave Station 1
M8160
Slave Station 17
M8141
Slave Station 2
M8161
Slave Station 18
M8142
Slave Station 3
M8162
Slave Station 19
M8143
Slave Station 4
M8163
Slave Station 20
M8144
Slave Station 5
M8164
Slave Station 21
M8145
Slave Station 6
M8165
Slave Station 22
M8146
Slave Station 7
M8166
Slave Station 23
M8147
Slave Station 8
M8167
Slave Station 24
M8150
Slave Station 9
M8170
Slave Station 25
M8151
Slave Station 10
M8171
Slave Station 26
M8152
Slave Station 11
M8172
Slave Station 27
M8153
Slave Station 12
M8173
Slave Station 28
M8154
Slave Station 13
M8174
Slave Station 29
M8155
Slave Station 14
M8175
Slave Station 30
M8156
Slave Station 15
M8176
Slave Station 31
M8157
Slave Station 16
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