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150
Bus Parameters
Appendix A
The parameters to calculate are:
• Target Rotation Time
• Min Slave Interval
• Watchdog timeout
• Data Control Time
These four values depend on the number of slave stations allocated to the PROFIBUS-DP Master Unit, the
number of I/O bytes each of the slave stations will exchange with the Master Unit, and how many other Master
Units are on the PROFIBUS network at the same time.
Furthermore, the Unit will require additional time to process the PROFIBUS I/O data and exchange this with
the PLC CPU. Based on this, the following empirical formula is used:
Min. Slave Interval = A
1
+ (B
1
* slave stations) + (C
1
* bytes to transfer) +
(bits per
µ
s)*((A
2
* slave stations) + B
2
* modules) + (C
2
* Words to exchange)
[1]
Target Rotation Time T
TR
=
å
(Min. Slave Interval)
[2]
T
WD
= T
TR
+ 20000
[3]
Data Control Time = (T
WD
* 7) * 100 / Baud rate
[4]
Based on measurements, the following values have been determined for the 6 factors in equation [1]:
Summary of Contents for SYSMAC CJ1W-PRM21
Page 2: ...iv...
Page 36: ...22 Basic Operating Procedure Section 1 5...
Page 52: ...38 Defining PROFIBUS DP in the Software Section 2 5...
Page 112: ...98 Allocated CIO Area Words Section 4 2...
Page 122: ...108 Command Response Reference Section 5 2...
Page 160: ...146 Replacing the Unit Section 7 8...
Page 174: ...160 Appendix...
Page 180: ...166 I O Data Conversions Appendix D...
Page 186: ...172 Configurator Error and Warning Messages Appendix E...
Page 187: ...173 Index...
Page 188: ...174 Index...
Page 190: ...176 Revision History...