ABB NIBA-01 Installation And Startup Manual

Contents

ABB NIBA-01 Installation And Startup Manual Manual pdf 24 page image

Chapter 5 – Programming5-4NIBA-01 Installation and Start-up GuideCalculating the OptimalCycle (Scan) TimeFor fast data transfer, the host controller should sent the messageframe (detailed in Chapter 6) as frequently as possible. However, theslave stations on the bus may not be able to follow if the cycle time(scan time) is too short. The cycle time can be calculated using thefollowing formula:t cycle = ( 13 • ( 6 + n ) + 1.5 • m ) • tBit + t SW + t PHwheret cycle Transfer time in millisecondsn Number of user data bytesm Number of remote bus modules installedt Bit Bit duration (0.002 ms for 500 kbit/s)t SW Software runtime (0.2 ms)t PH Runtime on the transmission medium(for copper, 0.016 ms • l/km,where l = remote bus cable length in kilometres)Note: The minimum cycle time with the NIBA-01 is 1 ms.