Maximum Outstanding Messages

If multiple messages is enabled, the following global parameter is used to define the maximum number of outstanding messages that can be sent.

  • S90TCP_MAX_POLL_MSG
  • <PORT>_MAX_POLL_MSG
  • <DEVICE>_MAX_POLL_MSG

S90TCP_MAX_POLL_MSG

For Project
Purpose To define the maximum number of outstanding messages that can be sent to all devices on all ports in the project.
Value 1 to 64
Default Value 1

<PORT>_MAX_POLL_MSG

Where <PORT> is the number of the port.

For Port
Purpose To define the maximum number of outstanding messages that can be sent to all devices on a specific port within the project.
Value 1 to 64
Default Value 1

<DEVICE>_MAX_POLL_MSG

Where <DEVICE> is the name of the device.

For Device
Purpose To define the maximum number of outstanding messages that can be sent to a specific device.
Value 1 to 64
Default Value 1

The following table identifies the order of precedence for valid globals.

Global... Supercedes
Device-level Port-level
Port-level S90TCP-level
S90TCP-level Default
Note: As long as the communication load is within the capability of the Series 90-70 (as it is configured with the existing PLC application), communications remains reliable without dropouts. If the communication load is beyond the capability of the Series 90, then there may be loss of communications or it may be observed that the Triplex interface will switch between viable communication paths. If this occurs, reduce the number of concurrent messages.

When confirming that the number of concurrent messages chosen is compatible with the PLC application, be sure to validate the application with the Series 90-70 in run mode running the complete PLC application.