Description of the problem

A customer feedback 28-PIU reported single board not in position alarm (BD_STATUS) with alarm parameter 0xff 0xff 0xff 0xff 0xff 0xff.

The alarm still exists after 28-PIUB is plugged in, and the alarm still exists after a new PIU board is replaced.

PIUB power supply board alarm lamp status is normal, the alarm still exists.

Test the voltage of the power supply board with a multimeter, the voltage is normal.

Host version: 5.21.18.50P01

73461 28 BD_STATUS MJ start 2013-11-20 12:23:56 None 0xff 0xff 0xff 0xff 0xff 0xff 0xff

Process

The following is the schematic diagram of BD_STATUS reported by the PIU single board:

The two masters judge whether the PIU is online or not by detecting the level of the PIU in-place signal line, but the BD_STATUS alarm is reported only when the main master detects that the in-place signal line is at a high level, and the standby master detects that it will not be reported. Assuming that the PIU in-bit line level is V, then:

1, when the device is plugged with dual masters, but not plugged with PIU, V=VCC, the main master detects a high level and reports BD_STATUS.

2、When the device has dual masters plugged in and there is a PIU inserted, V=VCC*R1/(R2//R3+R1), R2//R3 indicates the resistance of R2 and R3 in parallel.

At this time, normally V is low, the main master detects as low and does not report the BD_STATUS alarm.

However, if R2 or R3 resistor is abnormal, causing R2//R3 resistance to become small, then V will increase, causing the main master control to detect a high level on the bit line and report BD_STATUS alarm.

Solution

From the previous customer operation and voltage measurement, it can be confirmed that the PIU is normal, only the main control board to monitor the PIU has a problem, will not affect the power supply work.

1, the customer plugs and unplugs the AUX alarm, which still exists, while checking the slot no inverted pins;

2, a line to pull out 28-PIU, checking the slot found that there is no inverted pin;

3, a line pull out the 18-slot backup main control board, found that the slot does not have a pin, the alarm disappeared, so replace the single board.

Recommendations and summary

According to the alarm schematic above, it can be seen that there are only four parts that affect the PIU in place line: 1, the PIU board itself 2, the backplane bus 3, the main master 4, the standby master (not related to the AUX and other boards)

As the PIU is no CPU does not record logs, it can only be based on the scope of the impact of a line of investigation to solve the problem.

1、Confirm whether the PIU is normal (whether the slot is inverted pin)

2, whether the backup master control is normal (whether the slot is inverted pin)

3、Main master control is normal or not (slot is inverted or not)

4、Mother board

This chapter of related technical information and SDH equipment troubleshooting process is collected and organized by Shenzhen Optical Transmission Network Technology Co. Our company specializes in Huawei SDH optical transmission equipment, SDH transmission equipment sales.