Rockwell Automation 1755-OF8 GuardPLC Controller Systems - Manual (Page 160)

160 Publication 1753-UM001C-EN-P - March 2010
Chapter 16 Peer-to-peer Communication Overview
Production Rate (ProdRate)
ProdRate is the minimum time interval between two data messages.
The purpose of ProdRate is to limit the amount of data to a magnitude
that can be transported to the recipient without overloading a (slow)
communication channel. This results in an even load on the
communication channel and avoids the reception of outdated data.
Watchdog Time (WDZ)
Watchdog Time is the maximum permissible duration of a Run cycle
on a PES. The Run cycle depends upon the complexity of the user
program and the number of peer-to-peer connections.
Worst-case Reaction Time (T
R
)
Worst-case Reaction Time is a safety-relevant application parameter. It
is the time between the occurrence of a physical input signal change
at PES
1
and the corresponding physical output signal change at PES
2
.
Worst-case Reaction Time (T
R
)
≤
t
1
+ t
2
+ t
3
+ t
4
TIP
A production rate of 0 means that a data message can be
transmitted with each cycle of the user program.
Worst-case Reaction Time Variables
Variable Definition
t
1
The worst-case time for the user program on PES
1
to process the input
signal and prepare the data for transmission.
2 x WDZ (PES
1
)
t
2
The additional transmission delay on PES
1
.
Equals 0 ms, if the ProdRate is 0.
Otherwise: equals ReceiveTMO + WDZ (PES
1
)
t
3
ReceiveTMO
The maximum age of a message when received at PES
2
.
t
4
The maximum time for the received data message to be processed by the
user program on PES
2
and the output signal to be set.