ControlLogix: Addressing by memory location

[jreimerddauto]

Im trying to figure out how to use indirect addressing of memory locations to create a "for loop"-like function that would walk through every in-scope tag of a PLC, read its value, and write it serially.

For example, I want the serial-slave device to request the value at address 0x00, receive it, record it, request the value of memory location 0x01, etc etc.

How would I go about doing this in a ControlLogix system?

From what I know so far, to do this in ControlLogix, I would have to manually create a list of every tag I wanted to record and pass it from either master-slave or slave-master.

In C (which I haven't touched in years, forgive my syntax) it might look something like;

for(i = start;stop;step)
{
&ptr = ;
write_to_serial = (*ptr)
}

 

[Dravik]

Well, you could use a For loop in STL and iterate through your UDDT.
Caveat here - I don't know how long your comms will take and this will lock that routine up till it is done.

 

[Ken Roach]

It sounds a little like you're attempting to perform a memory table read, bypassing the structures of the Tag Database.

Is there a reason this interface with another device couldn't be done with a serial protocol like DF1 or Modbus ?