online debugging with gx developer fx

[Guest Guest_jerrycat]

i,m trying to debug a program using gx developper fx, when i do a device test on an input device when the plc is in run , the input let corresponding to that device does not lit, nor can is the device turn on on my monitoring sreen, can some tell me how device test work when the plc is in run . when the plc is in stop i don,t have this problem. when i forcibly turn an input device that led is lit.

[panic mode 246]

There are some good tutorials you should read before you go too far. Please register and read a bit in this section. You won't be dissapointed....

[jerrycat 0]

panic mode i,m already a member, just didn,t lock in at that time i know that when you force a input when the plc is in run mode , that input turn on for a fraction of a second then it go off again . i m wondering if their is way to force an iput to stay when then plc in run mode. i know that you can do that when the plc is in stop. can you help me out here

[Crossbow 294]

With Mitsubishi, forcing inputs on is not possible (or so I was told). You cannot force an input if there is an actual input point with that address. For testing what I've done in the past is to parallel my inputs with M bits, and then force the M bits. Then when done testing, you can remove the M bits from the program or leave them for future troubleshooting.

[panic mode 246]

Actually forcing inputs in Mitsubishi is a bit of delicate topic. Mitsubishi "force" is actually only "toggle". Bit that is used in scanned logic will cancel any "force". Inputs behave differently: You can force high inputs which are currently low. You cannot force low inputs which are currently high. There is no indication (memory bit in system area or CPU LED) to show that there are active forces. There is no function in Mitsubishi PLC programming software that can search and display forced inputs either. If you do this on running machine be very careful because it's just too easy to forget one or two forces and eventually this might cause real disaster. The simplest way to clear forces is to power down or reset CPU. The safest way is not to force inputs. You could probably dedicate area in PLC memory that can be mapped to inputs and then use something like BMOVk4M500 K4X0 K8 to overwrite X devices on begin of scan. I never tried it (never needed it - there are different ways to test program and commission equipment...)

[jerrycat 0]

Thanks you all , i though real force was possible with mitsubishi, i think i will monitor my program using gx simulator only, many thanks