B&B Electronics I-7060 - Quick Start Guide User Manual
Page 53
Getting Started
for I-7000 Series Modules
Date: Jan-08, 2002 Version 1.02 page: 53
Q: What is the maximum scan-rate in the RS-485 network?
A:
The scan-rate depends on the baud rate of the RS-232 COM port,
checksum status, module numbers, channels, commands to send, result
string received and system performance.
To test, use those conditions:
I-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 communication: Command string + Result string
= 14 Chars = 140 bits
140 (bits/communication) / 115200 (bits/sec)
= 0.00122 (sec/communication)
Hardware delay (every communication): 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 lets the OS process other tasks. This may
reduce the program performance.