User's Manual

Teklogix 9150 Wireless Gateway User Manual 197
Chapter 7: 9100 Monitoring/Diagnostics
Fault Monitoring
7.1 Fault Monitoring
Once power to a port is applied, the microcontroller enters a fault monitoring mode.
The diagnostic functions are:
• Low current condition
• High current condition
• Power Monitoring (conducted regardless of port state)
7.1.1 Low Current Detection
The microcontroller continuously checks ports in the “ON” state to determine if
each/any is in an under-current condition (this will typically happen when the Ether-
net cable is disconnected or some other fault occurs). This ensures that a powered
cable, when disconnected from a powered device, cannot be reconnected into some
other device, possibly causing damage to a non-compliant device.
If a Low Current condition is detected, then the power to the port is turned off. This
process is carried out for each of the four ports during fault monitoring. Following a
Low Current detection, the 9100 starts the discovery process again after a two-
second delay.
This fault is indicated by a slowly flashing yellow LED. After a two-second delay,
the 9100 will start the resistor detection again.
7.1.2 High Current Detection
Once a port is enabled, a sense voltage is measured periodically by the microcon-
troller to ensure that it remains less than the maximum allowed voltage, otherwise
an over-current fault occurs. A maximum continuous current of up to 350 mA is
allowed. To allow for inrush currents, which may occur when a powered device is
first connected (or the presence of a short or surge on the line), a hardware current-
limiting circuit ensures fail-safe output power control during the first 100mS follow-
ing port power-ON. Subsequently, the microcontroller will turn the port power OFF
immediately upon detection of an overcurrent condition.
Note: There is a five-second safety period before the 9100 begins resistor detec-
tion on a port that has triggered the overcurrent detection.