Quick Eagle Networks DL3800E manual E1 Port Crossover Detection

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When the incoming signal is framed on the inverse mux frame, the framer will start loading its Dual Port RAM. The address to the Dual Port RAM is derived from the 16-bit inverse mux frame. The software will ask all framers to latch their Dual Port RAM addresses at the same time, and by looking at the addresses, the software can determine which network has experienced the greatest delay.

From the receive inverse IMUX framer, the incoming data will go to the receive multiplexer. The net that is last in time will be enabled to tell the receive multiplexer when to start unloading the Dual Port RAM to the DTE interface. To allow for jitter and wander specifications, the read address counter will be positioned approximately three frames behind the write address for the network last in time.

E1 Port Crossover Detection

When the IMUX E1 circuits synchronize, they use the IMUX framing to communicate to know the ports (1-8). A crossover is a situation where a network line is connected to a port on the remote 3800E different from the port it originates from on the local 3800E.(e.g. port 1 on the local unit is connected to port 2 on the remote unit). This situation will cause DTE traffic to be incorrectly multiplexed and, as a result, severely errored.

When a crossover is detected, the DL 3800E removes the crossed port from the DTE data bundle and reduces the DTE data rate. The LED will change to flashing green and the port status in the Alarms & Status menu read “Line crossed”, and also (Crossed to port:x), where x is the port number connected at the remote end. It also generates an SNMP alarm: enCrossoverAlarm.

When the crossover is cleared, the port is restored to DTE bundle and the LED restores to green. Port crossover status clears and the SNMP alarm enCrossoverAlarm is idled.

An IMUX E1 circuit is reestablished as soon as the mismatched circuits are disconnected and reconnected properly.

Figure 2-3is a functional schematic of the DL3800E unit showing a unit supporting four E1 lines.

Introduction 2-5