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I-7000 Remote I/O 015 Q.What is the maximum scan rates in the RS-485 network? ¡@ Ans: The scan rate depend on the BAUD RATE of RS-232 COM port, Checksum status, module numbers, channels, command to send, result string that received and system performance.
For those environment to test: 7012 module: x 1 Channel: x 1 Baud Rate: 115200 bps Command: #AA (cr)(null) ==> 5 Chars Result: >SDDDDDD (cr) ==> 9 Chars
1 Char: 1 Start bit + 8 Data bits + 1 Stop bit = 10 bits Every communications: Command string + Result string = 14 Chars = 140 bits 140 (bits/communication) / 115200 (bits/sec) = 0.00122 (sec/communication) Hardware delays (every communications): 1 mSec Scan rate: 1/ (0.00122 + 0.001) = 450 (communication/sec)
Estimated scan rate: 450 times/sec maximum.
Tested value of scan rate: 440 times/sec maximum without system message processing. 360 times/sec maximum with system message processing.
Note: System message processing is meant let the OS to process other tasks, this may reduce the performance of this program. ¡@
Written by David Chen Date:2002/12/24 |
