peb2265 ETC-unknow, peb2265 Datasheet - Page 13

• Manufacturer Part Number: peb2265
• Description: Channel Codec Filter With Iom -2 Interface Iom -2 Sicofi -2
• Manufacturer: ETC-unknow

2.1.1
The analog input signal has to be DC-free connected by an external capacitor because
there is an internal virtual reference ground potential. After passing a simple antialiasing
prefilter (PREFI) the voice signal is converted to a 1-bit digital data stream in the
Sigma-Delta-converter. The first downsampling steps are done in fast running digital
hardware filters. The following steps are implemented in the micro-code which has to be
executed by the central Digital Signal Processor. This DSP-machine is able to handle
the workload for all two channels. At the end the fully processed signal (flexibly
programmed in many parameters) is transferred to the IOM-2 interface in a
PCM-compressed signal representation.
2.1.2
The
PCM-law-pass-filtering, gain correction and frequency response correction are the next
steps which are done by the DSP-machine. The upsampling interpolation steps are
again processed by fast hardware structures to reduce the DSP-workload. The
upsampled 1-bit data stream is then converted to an analog equivalent which is
smoothed by a POST-Filter (POFI). As the signal VOUT is also referenced to an internal
virtual ground potential, an external capacitor is required for DC-decoupling.
2.1.3
There are two loops implemented. The first is to generate the AC-input impedance (IM)
and the second is to perform a proper hybrid balancing (TH). A simple extra path IM2
(from the transmit to the receive path) supports the impedance matching function.
2.1.4
There are four analog and five digital test loops implemented in the IOM-2 – SICOFI-2.
For special tests it is possible to “Cut Off” the receive and the transmit path at two
different points.
Semiconductor Group
digital input
Transmit Path
Receive Path
Loops
Test Features
signal is received
13
via the IOM-2 interface.
IOM
®
-2 – SICOFI
®
-2 Principles
PEB 2265
Expansion,
1997-07-01