Rockwell Automation 56AMXN/B ControlLogix AutoMax Comm Module - Manual (Page 68)

Page 68 AutoMax DCSNet /RE RIO Module
Publication number 56AMXN-UM002A-EN-P November 2002
DCS Network Update Time
From the manual for the 57C404B (publication J2-3001-3), 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 sendinga message, this is 2.09 ms. If a slave
is sending a message, this is 3.395 ms.
For example, a network composed of 10 drops which is not messaging
will update each drop with a period of:
UpdateTime = 2.99 * 10 + 2.48 = 32.38 ms