This is has been very rare. On power-up the 5387 board occasionally seems to report a large number of encoder counts, usually negative. The number of counts is far larger than anything that could physically occur on a machine. This is has been very rare. On power-up the 5387 board occasionally seems to report a large number of encoder counts, usually negative. The number of counts is far larger than anything that could physically occur on a machine.

Since we have a large number of 5387 boards in the field that would be very difficult to update, this change attempts to detect the problem and ignore the erroneous counts if and when they occur. Prior attempts to read the encoder several times on power-up to throw away any encoder counts occurring during power up have failed, leading us to believe the timing of the issues is complicated. For this reason we are adding a test that we expect will capture and correct the issue no matter when it occurs.

If the number of counts (positive or negative) exceeds 10,000 on a single read the encoder counts are discarded. This number, despite the appearance of being a nice round number pulled out of the air, was actually calculated using the following rational. A maximum material rate of 2000fpm using the smallest allowable resolution of 0.00004" and an encoder sample rate of 1msec results in a maximum number of counts per 1msec of 10,000 counts.