Questions about the Siemens 315-2PN/DP CPU
Thread Content
The existing control system uses a Siemens 315-2PN DP CPU, which has been functioning properly. Today, communication with the upper-level computer was suddenly lost; the lights on the CPU were flashing. After powering it off and then turning it back on, normal operation was restored, but all the set points for upper and lower limits were reset to zero, requiring them to be set again. What could be the problem?
All upper and lower limit settings are reset to zero; this is likely part of the initialization process. However, generally, the upper and lower limits are converted using FC105, and they represent constants. Look, is this being displayed through Memory communication?
When communication is lost and the CPU light flashes, there is likely a fault present; however, to determine exactly what the fault is, it is necessary to check the diagnostic information online at that time. Turning off the power and turning it back on restores normal operation; this merely masks the fault temporarily. In principle, the system will stop working again once the fault conditions reoccur. The upper and lower limits being reset to zero is due to the limit values not being properly initialized after a cold start.
Under this system, there are 10 CPU stations with a capacity of 200 each (these are the CPUs of 10 vacuum units, communicating via EM277). Occasionally, some of these units lose power and need to be repaired, and as a result that station is lost; in such cases, the CPU315 keeps reporting a BF error, yet the system continues to function normally. Could the fault that causes the CPU to shut down be related to the CPU operating with faults for an extended period of time?
Under this system, there are 10 CPU stations with a capacity of 200 each (these are the CPUs of 10 vacuum units, communicating via EM277). Occasionally, some of these units lose power and need to be repaired, and as a result that station is lost; in such cases, the CPU315 keeps reporting a BF error, yet the system continues to function normally. Could the fault that causes the CPU to shut down be related to the CPU operating with faults for an extended period of time?
I haven’t used it, so I’m not sure. Diagnostic information can be viewed online when a fault occurs. In the Profibus communication method based on a master-slave structure, when it comes to a station that has failed to respond, the system waits until the timeout period expires before moving on to the next station, which results in slower communication. It is possible to consider keeping the PLC powered during unit maintenance.