peb20550 Infineon Technologies Corporation, peb20550 Datasheet - Page 238

• Manufacturer Part Number: peb20550
• Description: Extended Pcm Interface Controller
• Manufacturer: Infineon Technologies Corporation

PEB 2055
PEF 2055
Application Hints
5.9.2.2 Small PBX
Figure 83 shows a realization example of a small PBX. If the total number of lines
(internal or external) is smaller than the capacity of the EPIC (32
(2
B + D) or 64
B),
the PCM interface of the EPIC need not to be connected to a switching network since all
the B (and D) channel switching can be done inside the EPIC. In this special case, it is
sufficient to apply only a PCM clock to the EPIC, the PCM frame synchronization signal
(8 kHz) can be omitted. The IOM-2 clock and framing signals DCL and FSC are still
generated correctly by the EPIC. The STAR:PSS bit should then not be evaluated: it
stays at logical 0 all the time.
The PBX shown in the figure 83 offers 8 analog (t/r) subscriber lines, realized with two
quadruple codec/filter devices SICOFI-4 (PEB 2465). These can of course be replaced
by any IOM-2 compatible layer-1 device if digital lines are required. Any mixture of
codecs and digital layer-1 devices is also feasible.
The figure 83 also shows a digital trunk line (external line) which is realized with a U
-
k
layer-1 device, IEC-Q (PEB 2091), operated in NT-PABX mode. The PBX can therefore
be connected directly to the U
interface coming from the CO. The NT-PABX mode of
k
the U
- layer-1 devices is similar to the LT-T mode of the S layer-1 devices: in both cases
k
the layer-1 device delivers a reference clock which is synchronous to the received S or
U
- frame and that can be used to synchronize the local PBX clock generator. Any phase
k
differences between the local IOM-2 frame and the received S or U
- frame are
k
compensated by an elastic buffer inside the layer-1 devices.
Since the digital trunk line also needs a D channel handler, an ISDN Communication
Controller (ICC; PEB 2070) is assigned to that IOM-2 channel.
Semiconductor Group
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