scheduled interrupt with devicenet

[mr_shadow 0]

Hi all; I'm trying to collect some data from an analog unit which is replaced in a devicenet network node,my cpu is CS1-H, i want to get the samples for ex: with 30 ms interval, but my plc program cycle is totally for ex:100 ms, so i thought it and i can do it may be with a scheduled interrupt with interval at 30 ms , but i don't know how to refresh the CIO for the analog input slave unit ,i read the CJ1G programming manual and i saw an instruction "DLNK" CPU BUS UNIT I/O REFRESH. If i write this in the scheduled interrupt task can i refresh the inputs regardless to the cpu total cycle time and like this can i get the analog values with 30 ms interval? If this is not possible with this method ,by another method can i get the data with a higher speed than total plc cycle? If yes how? Can anybody help me? Note: Changing an reducing the program cyle time is possible but the program is inside in a running machine i don't have much time to write it again

[Sleepy Wombat 27]

Do you have any idea of the device net comm's time ? IE how many slaves (nodes) and what is the maximum number of the slave unit ID. Also what Device net analogue card (device net) are u using ? Are you just storing the data in the PLC ? With a scan time of 100ms and the precautions of executing the DLNK instruction i am not sure that it will work.

[Harald_Brueck 0]

Hi, I think, nobody tried to use scheduled interrupt for DeviceNet slaves before. Try to reduce the cycle time of the PLC. You have to identify, where the huge cycle time comes from. Old C200H units used? Floating Point maths used extensively? Instructions, that may be processed in the background? Try to devide the whole program in 3 tasks (prgram1,program2,program3) program1 you will always execute and do all the things, which are urgent; the rest of the program you execute only the half , every second cycle: cycle 1: program1, program2 cycle 2: program1, program3 cycle 3: program1, program2 cycle 4: program1, program3 and so on Harald