CN8380 Datasheet, PDF (41/91 Pages) Conexant Systems, Inc – integrated quad line interface unit unit for both 1.544 Mbps (T1) and 2.048 Mbps (E1) applications

CN8380
Quad T1/E1 Line Interface
2.0 Circuit Description
2.4 Transmitter
2.4.7 Transmitter Output Monitoring
2.4.7.1 Short Circuit
Detect
The transmitter output pulse is monitored and a short circuit is detected when the
amplitude falls below an internally determined threshold for approximately 64-bit
times. The short circuit state deactivates when the amplitude rises above a second
threshold for 64-bit times.
When a short is detected, the line driver current is reduced to approximately
50 mA peak, as measured on the line side of the transformer. Typically, this is
caused by a transmit cable short circuit or by a transmission line transient current
surge. In Host Mode, short circuit activation sets the TSHORT bit in the Alarm
Status register [ALARM; addr n5] and in the Interrupt Status Register [ISR; addr
n6]. No indication of short circuit is available in Hardware Mode.
2.4.7.2 Driver
Performance Monitor
The DPM monitors the line driver output signal for valid signaling activity. The
output signal is monitored for pulse level, invalid AMI coding, pulse density, and
stuck signals. In Host Mode, a DPM fault condition sets the TLOS bit in the
Alarm Status register [ALARM; addr n5] and in the Interrupt Status Register
[ISR; addr n6]. In Hardware Mode, the four internal DPM status indicators are
combined (logical NOR) and output on the IRQ pin.
If the transmit driver is disabled (XOE = 1), the DPM is available for
monitoring a transmit signal from an external source. In this mode, XTIP[n] and
XRING[n] are used as inputs and can be connected to the transmit outputs of
another CN8380 channel or device.
N8380DSA
Conexant
2-19
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