ProSoft Technology AN-X-AMX - Manual (Page 30)

Page 26 AN-X-DCSNet2 November 2011
AN-X supports RPIs from 5 to 750 ms.
Select an RPI appropriate to the DCS network scan time and to your
application. The approximate DCS network update time is 3 ms per
drop.
The DCS network update time is given by:
Update time = (DropTime * N) + NewDropTestTime + MessageTime
where
DropTime = the amount of time for a master to send a message and the
slave to respond = 2.99 ms
N = Number of slave drops (physical and virtual)
NewDropTestTime = amount of time for the master to poll an inactive
drop and wait for its response = 2.48 ms assuming no response
MessageTime = amount of time to transfer programming terminal
messages. If the master is sending a message, this is 2.09 ms. If a slave
is sending a message, this is 3.395 ms.
Example:
A network composed of 10 drops, with no messaging, updates each drop
with a period of:
UpdateTime = 2.99 * 10 + 2.48 = 32.38 ms