Hitachi EH-150 Applications Manual page 16

3) Precautions related to assignment duplication
(
Link areas assigned in local stations will become the areas for transmitting to other stations, and the
remaining area will become the area for receiving from other stations, in accordance with link area
assignment. Owing to this, it is not possible to duplicate assigned areas on the same link system. A link area
duplication error will be trigger is duplication does occur.
The same applies to link systems in which the first link and second link area are mixed. In this event, ensure
that the first digit of the L, WL and DL numbers are not duplicated.
A duplication error will be triggered if the link areas are duplicated owing to a link started up after link
operations are in progress, and link operations for the station in which the duplicated link area has been
assigned will be terminated. The link operation status flag will be set at OFF in this case, but the link
participation flag will not be set at OFF. Also, the link area data existing immediately prior to the error will be
saved.
(4) Link area data
Data is read into the local station area in accordance with user programs during normal operations. This
data can be amended if necessary and transmitted to other stations at refresh time intervals.
On the other hand, the contents of other station areas will be updated by the data transmitted from other
stations at refresh time intervals. The details of the data transmitted from other stations are notified to the
user when the contents are read with the user program.
Note: that it is not possible to set the link area for power cut storage.
(5) Precautions related to link area data
1) When the power supply to the local station is switched on
All data in the link area will be cleared by the system when the power supply is switched on. In addition to
this, the execution timing of the user program started with the CPU's RUN command and the CPU's link
module will participate in the link, and the data first transmitted from the local station to other stations at
the start of operations will differ in accordance with the timing for transmitting from the local station to
other stations and the time difference involved. The program should therefore be created while monitoring
the special internal output link's operation status flag and the CPU status flag.
2) When the local station's CPU is RUN
The transmission area's data will commence from the value first updated. As the receiving area's data
updates the data transmitted from other stations when the CPU is stopped during link operations in other
stations, the data will commence from the value received from other stations when the RUN command is
started.
Note: It is possible to clear the link area when the system is switched between RUN and STOP with the
CPU module's special internal output (WRF07E) setting. The data in the transmission area when this
setting is performed will commence from 0. (Refer to the CPU Module Application Manual for further
details on the WRF07E setting.)
3) When the local CPU is stopped
The transmission area will save the value most recently updated with the user program. In addition to this,
the link area in other stations will continue to update the data transmitted from other stations when the link
module is performing link operations. However, the area in other stations will save the data most recently
received if the link module stops link operations.
Note: It is possible to clear the link area when the system is switched between RUN and STOP with the
CPU module's special WRF07E internal output setting. The data in the transmission area when this setting
is performed will save 0. (Refer to the CPU Module Application Manual for further details on the WRF07E
setting.)
4) When the power supply to the other stations is set at OFF, and when link operations are halted in
other stations
The receiving area in the local station will save the data most recently transmitted from the other stations
without amendment.
Chapter 4. Basic CPU Link Operations
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