Rockwell Automation 1785-Lxxx Enhanced and Ethernet PLC-5 Programmable Controllers - Manual (Page 148)

Publication 1785-UM012D-EN-P - July 2005
9-16 Communicating with Devices on a DH+ Link
Average DH+ Link Response Time Test Results
This section shows graphically the results of testing performed on a DH+ link
where the number of stations and words sent in the message varies.
The figure below shows the average response time of messages of varying
sizes on a DH+ link with a varying numbers of stations. It also gives you an
idea of the typical response time you can expect on a given DH+ link.
Test Setup
One to 22 PLC-5 controllers were used with one
personal computer online. Each PLC-5 controller
executes 1K of ladder logic.
Initial testing was done with one PLC-5 controller
writing data to another PLC-5 controller. The
response time was recorded. Additional PLC-5
controllers were added to the network, each
writing the same amount of data to a PLC-5
controller at the next highest station address.
Four separate tests were run using data
transmissions of 50, 100, 250, and 500 words.
Number of PLC-5 Processors
Response
Time
(Sec)
50 W
100 W
250 W
500 W
+
X
W=Words
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
+ +
+
+ +
+
+
+
+
+
X
X
X
X
X
X
X
X
X
X
Number of Controllers