All variables associated with a process control channel (for example: Kp, T_FILT, ...) are in default read and/or write.
A channel (%CH r.m.c) must be associated to an
IODDT-type variable. The purpose of such a variable is to simplify explicit reads and writes. The variable allows the following operations :
Explicit instructions are applied to the language object of the i channel with the IOODT-type variable LOOP_i.
Example 1: sending an auto-tune instruction to the first loop of a loop controller with 3 single loops. The word being sent contains the explicit command affecting the control loop. The IODDT is of the T_PROC_3SING_LOOP type.
There is no limit to the number of commands in a PLC cycle. Acknowledgment of the instruction and updating of the states of the process control channel concerned come into effect on the task's next cycle.
NOTE: Instructions associated with the operating mode of the loop controller (Auto, Manu, Tracking, Auto-tuning) may not be sent at the same time as part of the same cycle (only the last instruction carried out in the cycle is recognized). In contrast, additional instructions (such as Remote, freeze Totalizer function, etc.) may indeed be sent as part of the same cycle.
Example 2: Manu mode transmission to the slave loop of a cascade-type channel. where LOOP_i is an IODDT-type variable. The IODDT in question may be of the T_PROC_CASC_LOOP type for a cascade-type control loop.
Command parameter or selection word (%MDr.m.c.j) values.
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Auto-selector loop
PARAM_COMMAND (%MDr.m.c.12) = 1 main loop
PARAM_COMMAND (%MDr.m.c.12) = 2 secondary loop
PARAM_COMMAND (%MDr.m.c.12) = 4 global loop
As the process loop includes only one loop, the %MDr.m.c.12 command parameter has no significance.
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3 single-loop loop controller
PARAM_COMMAND (%MDr.m.c.14) = j profile j j ={1, 2, 3}
