STANDARD PRODUCT
PM4351 COMET
DATA SHEET
PMC-1970624
ISSUE 10
COMBINED E1/T1 TRANSCEIVER
9
FUNCTIONAL DESCRIPTION
Receive Interface
9.1
Two basic receive options are available: the receive stream is presented as a
TTL-compatible unipolar signal with an associated clock, or the receive data is
reconstructed from unequalized pulses from a center tapped signal transformer.
See Figure 5 for the recommended external analog circuitry.
When the digital receive interface is enabled, the RDAT signal is expected to
carry a decoded serial bit stream. RDAT can be sampled on either the rising or
falling RCLKI edge. The polarity of RDAT can also be inverted.
The analog receive interface is configurable to operate in both E1 and T1 short-
haul and long-haul applications. Short-haul T1 is defined as transmission over
less than 655 ft of cable. Short-haul E1 is defined as transmission on any cable
that attenuates the signal by less than 6 dB.
For long-haul signals, unequalized long- or short-haul bipolar alternate mark
inversion (AMI) signals are received as the differential voltage between the
RXTIP and RXRING inputs.
For short-haul, the slicing threshold is set to a fraction of the input signal’s peak
amplitude, and adapts to changes in this amplitude. The slicing threshold is 67%
and 50% for DSX-1 and E1 applications, respectively. Abnormally low input
signals are detected when the input level is below 140 mV for E1 and 105 mV for
T1.
PROPRIETARY AND CONFIDENTIAL
32
PMC [ PMC-SIERRA, INC ]
