AB PLC Scantime and RPI

Folks, I am using a 1769-L36ERM and have I/Os over Ethernet. I am having issues with signal lag. The PLC get's a sensor input over Ethernet, does few calculations (under a separate program task) and sends an output over Ethernet to a Robot.

RPI of the Ethernet input = 5ms
RPI of the Robot = 20ms
PLC sub-program scan time = <1ms
PLC main program scan time about 10ms

There are 48 ethernet devices (yes, node number supported is maxed). The PLC scan time cannot be reduced any further. Will reducing the RPI help any? Apparently the robot is getting the signal few ms late. Thanks

this might be a wild goose chase - but check the PRIORITY of your tasks - and read the following:

http://forums.mrplc.com/index.php?showtopic=26162&view=findpost&p=125399

DISCLAIMER: I haven't had a chance to experiment with the model you've mentioned - but I've seen "issues" with other CompactLogix systems in the past ...