Hello all,
I am working on programming one of the PLC training modules we have at my work. It is a relatively simple assembly line model controlled by a Siemens S7-300 and a couple digital signal modules which control pneumatic solenoid valves. Connected to this system is an operator panel OP177B via Profinet, programmed with WinCC Flexible Advanced. I have created buttons on the operator panel for operation in manual mode, and can change the acquisition time associated with each tag (data block bit) linked to each button. A few questions:
1) I don’t exactly understand the process by which the PLC communicates i.e. sends/receives information to the operator panel (the process of the OP reading and writing data block bits to the data blocks via profinet). Can anyone explain how this works?
2) I have observed (at least it seems to be the case) that data block bits linked with buttons on the operator panel are updated based on the acquisition time specified in the tag details. I have a situation in my mode selection code where I say “if x conditions and jog bit not set, then manual mode” and in another network, “if x conditions and jog bit set, then jog mode” (the jog bit is toggled by an operator panel button). If these OP buttons were normal hardwired switches/buttons this would be fine, since their values would be read once at the beginning of the cycle and there would be no way for both modes to active at the same time. However, if the jog bit can be changed in the middle of the program by the operator panel, the situation could arise where during one scan both modes are active. Are the bits modified by OP buttons during a cycle be changed in the middle of the cycle? And if this is the case, is there a way to change this so that data block bits connected to buttons from the OP are only read once at the beginning of each scan, like a normal input?
Thanks for any info.
I am working on programming one of the PLC training modules we have at my work. It is a relatively simple assembly line model controlled by a Siemens S7-300 and a couple digital signal modules which control pneumatic solenoid valves. Connected to this system is an operator panel OP177B via Profinet, programmed with WinCC Flexible Advanced. I have created buttons on the operator panel for operation in manual mode, and can change the acquisition time associated with each tag (data block bit) linked to each button. A few questions:
1) I don’t exactly understand the process by which the PLC communicates i.e. sends/receives information to the operator panel (the process of the OP reading and writing data block bits to the data blocks via profinet). Can anyone explain how this works?
2) I have observed (at least it seems to be the case) that data block bits linked with buttons on the operator panel are updated based on the acquisition time specified in the tag details. I have a situation in my mode selection code where I say “if x conditions and jog bit not set, then manual mode” and in another network, “if x conditions and jog bit set, then jog mode” (the jog bit is toggled by an operator panel button). If these OP buttons were normal hardwired switches/buttons this would be fine, since their values would be read once at the beginning of the cycle and there would be no way for both modes to active at the same time. However, if the jog bit can be changed in the middle of the program by the operator panel, the situation could arise where during one scan both modes are active. Are the bits modified by OP buttons during a cycle be changed in the middle of the cycle? And if this is the case, is there a way to change this so that data block bits connected to buttons from the OP are only read once at the beginning of each scan, like a normal input?
Thanks for any info.