IAI America XSEL-S - Manual (Page 37)

Chapter 3 Operation (Construction for Network)
31
IA Net
XSEL-R/S
3.1.3 Regarding Communication Cycle Time
The communication cycle time is determined by the final station number of the connected units.
The communication cycle time (TS) can be expressed with the formula below.
TS [ms] = [(Final station number + 152) × (Final station number + 3) × 2] / 12000
TS indicates only the IA Net communication time, and does not show the total performance
including the execution time for SEL program and so on.
The communication cycle time for IA Net is shortened as the final station number is smaller.
The communication cycle time will get longer if the setting is established with some station
numbers skipped on the way or there is an unoccupied station number.
In IA Net, "resizing" is the method to change the final station number. Revise the network
construction and resize the final station number to minimize the number of the stations.
CAUTION It is recommended to leave some number of stations unoccupied to ease
future network configuration changes. (Example: if an XSEL is planned to
occupy only two stations, beginning at station 0, leave at least one
adjacent station, station 3, unoccupied). If no "spare," unoccupied
station(s) are left between stations in the initial network configuration, and
it becomes necessary to expand a controller's shared memory occupation
(add a station), then the station addressing of all controllers following that
controller in the network configuration will have to be shifted. Of course
the port addresses of input and output also shift, therefore the
programming also needs to be revised.