psf21911 ETC-unknow, psf21911 Datasheet - Page 40

• Manufacturer Part Number: psf21911
• Description: Isdn Echocancellation Circuit Terminal Applications Iec-q
• Manufacturer: ETC-unknow

Semiconductor Group
2.5
The U-interface establishes the direct link between the exchange and the terminal side
over two copper wires. Transmission over the U-interface is performed at a rate of
80 kBaud. The code used is reducing two binary informations to one quaternary symbol
(2B1Q) resulting in a total of 160 kbit/s to be transmitted. 144 kbit/s are user data
(2B + D), 16 kbit/s are used for maintenance and synchronization information.
The IEC-Q TE uses two differential outputs (AOUT, BOUT) and two differential inputs
(AIN, BIN) for transmission and reception. These differential signals are coupled via a
hybrid and a transformer to the two-wire U-interface.
Figure 16 shows a block diagram of the U-transceiver which can be subdivided in three
main blocks:
The System Interface Unit (SIU) provides the connection of the U- and the IOM-
interfaces. After scrambling/descrambling and rate adaptation the data channels (2B +
D) are transferred to the appropriate frame. Complete activation and deactivation
procedures are implemented, which are controlled by activation and deactivation
indications from U- or IOM-interfaces. State transition of the procedures depend on the
actual status of the receiver (adaptation and synchronization) and timing functions to
watch fault conditions. Two different modes can be selected for maintenance functions:
In the auto-mode all EOC-procedure handling and executing as specified by ANSI is
performed. In the transparent mode all bits are transferred transparently to the IOM-2
interface without any internal processing.
The Receiver block (REC) performs the filter algorithmic functions using digital signal
processing techniques. Modules for echo cancellation, pre- and post-equalization,
phase adaptation and frame detection are implemented in a modular multi-processor
concept.
The Line Interface Unit (LIU) contains the crystal oscillator and all of the analog
functions, such as the A/D-converter and the awake unit in the receive path, the pulse-
shaping D/A-converter, and the line driver in the transmit path.
Note: Due to the integrated microprocessor interface the IEC-Q TE V5.2 has a few µs
more delay from IOM-2 to the U-interface than the IEC-Q V4.4. This may be
relevant in very delay sensitive appplications like Radio in the Loop (RITL) and
Wireless PBXs.
U-Transceiver
SIU
REC
LIU
System Interface Unit
Receiver
Line Interface Unit
40
U-Transceiver
PSB 21911
PSF 21911
11.97