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3.3.3 Communication
Between a master station and intelligent devices, the master station cyclically reads input
data from the slave stations, and cyclically writes output data to the slave stations. Because
the specification of the DrvPIII drive is Version 1.10, cyclic transmission is supported.
Simultaneity of data
The DrvPIII drive communicates with a master unit using bit data of 64 input points (8 bytes)
and 64 output points (8 bytes) and register data of 8 input words and 8 output words when
two stations are occupied. In these 64-point data, the simultaneity of refresh data is not
always guaranteed depending on the type of the master unit. When using a fieldbus system, it
is important to take the simultaneity of data into consideration. For more detail, refer to the
instruction manual of the master unit used.
Delay in transmission data
When transmitting/receiving data between a master station and slave stations, data delay
may occur because of several factors. The following lists the possible major factors for delay
in transmission data until the instruction information from the master station is reflected in the
DrvPIII drive.
Transmission speed
The DrvPIII drive supports the transmission speeds listed below. The transmission speed can
be set by a #parameter value. The following shows the typical transmission time (link scan
time) values of CC-Link based on the number of connected units and transmission speed.
Supported transmission speed settings
The transmission speed of the DrvPIII drive can be set by [#119 CC-Link setup register] (bits
7-4). The actual setting is done by using the utility software. Note that because #119 is a
machine setup parameter, changes made take effect when the power is turned on next time.
The default setting is 10 Mbps.
Delay caused by the PLC and/or master unit such as the scan time
Delay caused by the CC-Link bus cycle time
Delay caused by the I/O refresh cycle of the DrvPIII drive (max. 1 ms)
10 Mbits/sec, 5 Mbits/sec, 2.5 Mbits/sec, 625 Kbits/sec, 156 Kbits/sec
Link scan time
(m se c )
6
5
4
3
2
1
0
20
40
Guideline of CC-Link Scan Time (10 Mbps at cyclic transmission)
[1] Remote I/O stations only
[2] Remote device stations only (when
all stations occupying one station)
[3] Local stations/intelligent device
stations only (when all stations
occupying one station)
60
No. of slave stations [units]
TI 71M01D06-01EN 3rd Edition: 2012.12.01
3-5
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