Remote I/O 015
Q.What is the maximum scan rates in the RS-485 network?
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.
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
Char: 1 Start bit + 8 Data bits + 1 Stop bit = 10 bits
Every communications: Command string + Result string
= 14 Chars = 140 bits
(bits/communication) / 115200 (bits/sec)
Hardware delays (every communications): 1 mSec
Scan rate: 1/ (0.00122 + 0.001) = 450 (communication/sec)
Estimated scan rate:
Tested value of scan rate:
times/sec maximum without system message processing.
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