![IDEC OpenNet series User Manual Download Page 301](http://html.mh-extra.com/html/idec/opennet-series/opennet-series_user-manual_617384301.webp)
21: D
ATA
L
INK
C
OMMUNICATION
21-8
O
PEN
N
ET
C
ONTROLLER
U
SER
’
S
M
ANUAL
Refresh Modes
In the data link communication, the master station sends data to a slave station and receives data from the slave station one
after another. After receiving data from slave stations, the master station stores the data into data registers allocated to each
slave station. The process of updating data into data registers is called refresh. The master station refreshes the received
data in two ways; separate refresh or simultaneous refresh mode. Differences of these two refresh modes are listed below:
When the data link system contains the
OpenNet Controller
and
MICRO
3
/MICRO
3
C
, set the baud rate to 19200 bps and
transmit/receive data quantity to 2 words in the Function Area Settings for the
OpenNet Controller
to communicate with
MICRO
3
/MICRO
3
C
stations.
When the
MICRO
3
/MICRO
3
C
is used as a slave station in the simultaneous refresh mode, the transmit frame from the mas-
ter station will be of a fixed data length. The
OpenNet Controller
master station in the simultaneous refresh mode automat-
ically checks if slave stations connected in the data link system are
MICRO
3
/MICRO
3
C
or not.
Separate Refresh Mode Communication Sequence
The master station can communicate with only one slave station in one scan time. When a slave station receives a commu-
nication from the master station, the slave station returns data stored in data registers assigned for data link communica-
tion. When the maximum 31 slave stations are connected, the master station requires 31 scans to communicate with all
slave stations.
Both master and slave stations refresh communication data in the END processing at each station. When data refresh is
complete, communication completion special internal relays M8140 through M8176 (slave station communication com-
pletion relay) go on at the master and slave stations for one scan time after the data refresh.
When the master station completes communication with all slave stations, special internal relay M8177 (all slave station
communication completion relay) goes on at the master station.
Mode
Separate Refresh Mode
Simultaneous Refresh Mode
Master Station
Scan Time
Since the master station refreshes received
data at the END processing of the user pro-
gram, the scan time in the master station is
affected.
Since the master station uses an interrupt pro-
cessing to refresh received data while executing
the user program, the scan time in the master
station is not affected.
Transmit Frame
All data of fixed data lengths are transmitted
as selected in the Function Area Settings.
Only data that has been changed is transmitted.
Master Station
Refresh Timing
Data received from one slave station is
refreshed at each END processing.
Data received from all slave stations is
refreshed at the END processing after complet-
ing communication with all slave stations.
Applicable Master
Station
OpenNet Controller, MICRO
3
, MICRO
3
C
OpenNet Controller
Applicable Slave
Station
OpenNet Controller, MICRO
3
, MICRO
3
C
OpenNet Controller, MICRO
3
, MICRO
3
C
Phone: 800.894.0412 - Fax: 888.723.4773 - Web: www.clrwtr.com - Email: [email protected]