If MPU is in a specific position on backplane as standby, its hot swap will reset the active MPU, causing the whole system to reset again.
The problem is caused by hot swap of standby MPU. In actual deployment and test, follow the standard strictly. Before drawing out the standby MPU, press the OFFLINE button on front panel of standby MPU for three seconds till the OFFLINE LED of standby MPU is red, indicating that the MPU is powered off; at the time, draw it out.
The problem is caused by hot swap of standby MPU. The pins of ZD connector on backplane are the same in length, and it is rare for MPU to match the backplane well, so the problem will occur because of the error in length of pins. The pins of ACT signal sent by active MPU leave first, and the other pins do not; at this time, the standby MPU is still being powered, and it detects the changes to ACT signals of active MPU; then it thought that the active MPU serves as standby, so it registers as active MPU automatically. Once the active MPU detects that the standby turns to active, it turns itself as standby. The active MPU will reset itsself once it acknowedges that it is standby, resulting in reset of the whole system.