A 000F0001 task error occurs if the input task is not allowed to run at least one every 100msec. This is a safety concern and the input task Watch-Dog timer generates a task error to shut the system down.

A 800004FF task errror is similar in that every task must be able to run at least once every 30 seconds. It is not as much of a safety concern because the high priority task that controll the machine are running but it indicates an infinite loop in the code somewhere and the system shuts down.

The tube mill has a scrap sensor input that is used to keep track of improperly welded sections of tube that need to be cut out and discarded. The scrap sensor is able to keep track of up to 100 sections of bad tube simultanously internally in its scrap queue ring buffer.

After a part is cut, the scrap queue has code that manages which sections of bad weld have been cut out. Once 100 sections of bad weld had been detected, this code had a bug in it that caused one of the indexes for the ring buffer to become corrupted and out of range. This resulted in an infinite loop. When running, the infinite loop was running in the Shear Task which is higher priority than the input task. The input task was not allowed to run and the input task Watch-Dog timer shut the system down.

During powerup, the same code executes but it executes prior to the input task starting. In this case the infinite loop code causes the 800004FF task error.

The bug was fixed and the Scrap Queue was tested throughout the 100 section range.