Rockwell Automation 1755-OF8 GuardPLC Controller Systems - Manual (Page 159)

Publication 1753-UM001C-EN-P - March 2010 159
Peer-to-peer Communication Overview Chapter 16
If the Receive]TMO is not
≥
2 x ResponseTime (minimum), the
availability of the Peer-to-Peer connection is guaranteed only in a
collision- and noise-free network. However, this does not result in a
safety problem for the CPU.
Resend Timeout (ResendTMO)
Resend Timeout is the safety-related monitoring time of PES
1
. If the
receipt of a data transmission is not confirmed by PES
2
within this
time period (ResendTMO), PES
1
repeats the data transmission.
Acknowledge Timeout (AckTMO)
Reception of data must be confirmed by the CPU with an ACK
(acknowledge) message to the sender of the data. If the CPU is busy,
ACK is delayed. Acknowledge Timeout is the maximum delay an ACK
message may have.
The AckTMO cannot be entered manually, but is set in conjunction
with a profile in the Peer-to-Peer Editor. For fast networks, AckTMO is
zero.
Queue Length (QueueLen)
QueueLen describes the number of messages that may be transmitted
without having to wait for an acknowledgement. It corresponds to the
network bandwidth and delay.
QueueLen cannot be entered manually, but is set along with a profile
in the Peer-to-Peer Editor.
TIP
The maximum permissible value for ReceiveTMO depends upon
the application and is set in the Peer-to-Peer Editor along with
the expected maximum ResponseTime and the profile.