CHAPTER 3: MAINTENANCE AND TROUBLESHOOTING
SNAP PAC S-Series User’s Guide
37
37
If the TCP/IP stack times out while trying to transmit data, it doubles the current RTO and tries again.
This process continues for five retries; after that, the controller stops trying and sends a timeout
message.
If you are receiving frequent timeout messages from the SNAP PAC S-series controller, you can
change the TCP parameters in PAC Manager.
1.
Choose Start
→
Programs
→
Opto 22
→
PAC Project Software
→
PAC Manager.
2.
In the PAC Manager main window, click the Inspect button
.
3.
In the IP Address field, type the IP address of the controller. Click Status Write.
CAUTION:
Note the following recommended settings:
If you set these fields too low, you may not be able to communicate with the controller at all, even
through PAC Manager, to fix the settings. Then you would have to reset the controller to factory
defaults.
4.
Change these four fields as necessary:
TCP Minimum Retransmission Timeout
sets an absolute minimum value for the RTO. The
controller’s calculated RTO will never go below this value.
TCP Minimum Retransmission Timeout (msec):
250
TCP Initial Retransmission Timeout (msec):
3000
TCP Retransmission Attempts:
5
TCP Idle Session Timeout (msec):
240,000
