I have a SLC 5/04 and PV1000 Standard
In the PV, these tags are defined:
Screen Status Tag = N7:44
Screen Control Tag = N7:43
In the PLC, when one particular alarm occurs, a value of 34 is moved to N7:43, via a one shot. This displays screen 34 as expected.
There is then a rung with the condition that when N7:44 = N7:43, CLR N7:43. The idea is obviously to return screen control to the HMI once the desired screen is displayed. This seems like it should work, but what is observed intermittently is:
Alarm occurs, PV displays screen 34, but PLC retains screen control and operator calls maintenance. I go online and see that N7:43 = 34 and N7:44 = 0.
Does anyone have any idea how / why the status tag can have a value of 0 when the screen being displayed is screen # 34?
Thanks for any help,
Rob
In the PV, these tags are defined:
Screen Status Tag = N7:44
Screen Control Tag = N7:43
In the PLC, when one particular alarm occurs, a value of 34 is moved to N7:43, via a one shot. This displays screen 34 as expected.
There is then a rung with the condition that when N7:44 = N7:43, CLR N7:43. The idea is obviously to return screen control to the HMI once the desired screen is displayed. This seems like it should work, but what is observed intermittently is:
Alarm occurs, PV displays screen 34, but PLC retains screen control and operator calls maintenance. I go online and see that N7:43 = 34 and N7:44 = 0.
Does anyone have any idea how / why the status tag can have a value of 0 when the screen being displayed is screen # 34?
Thanks for any help,
Rob