PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 62

• Manufacturer Part Number: PEF2091
• Description: ICs for Communications(ISDN Echocancellation Circuit)
• Manufacturer: Siemens Semiconductor Group

Semiconductor Group
the U transceiver can be subdivided in three main blocks:
3.4.1
The System Interface Unit (SIU) provides the link between the different interfaces of the
IEC-Q, e.g. IOM
Transmit Buffer
This block is a ’first in first out’ (FIFO) buffer which stores the user data (2B+D) given to
the IEC-Q via IOM
converter (LIU) and to the adaptive echocanceller (REC) with the appropriate U-interface
timing.
Receive Buffer
This is a ’first in first out’ (FIFO) buffer which stores the user data (2B+D) received from
the U-interface. These data are then transmitted to the user interface (IOM
the appropriate interface timing.
Scrambler / Descrambler
The scrambling and descrambling algorithms are implemented in these blocks (SCR and
DESCR in Figure 18, page 61). These algorithms ensures that no sequences of
permanent binary 0s or 1s are transmitted.
The algorithms used for scrambling and descrambling in LT and NT modes are
described in Figure 19. Note that one wrong bit decision in the Receiver automatically
leads to at least three bit errors.
SIU
REC
LIU
System Interface Unit
®
-2 to the U- interface.
®
-2 or µP interface. These data are then transmitted to the D/A
System Interface Unit
Receiver
Line Interface Unit
62
Functional Description
Data Sheet 01.99
®
-2 or µP) with
PEB 2091
PEF 2091