PEF2091 Siemens Semiconductor Group, PEF2091 Datasheet - Page 69

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

PEB 2091
PEF 2091
Functional Description
Embedded Operations Channel (EOC)
EOC-data are available in the U-frame at the positions M1, M2 and M3 thereby
permitting the transmission of two complete EOC-messages (2
12 bits) within one
U-superframe.
The EOC contains an address field, a data/message indicator (d/m) and an eight-bit
information field (see Table 10, page 68).
With the address field the destination of the transmitted message/data is defined.
Addresses are defined for the NT, 6 repeater stations and broadcasting.
The data/message indicator needs to be set to (1) to indicate that the information field
contains a message. If set to (0), numerical data is transferred to the NT. Currently no
numerical data transfer to or from the NT is required.
From the 256 codes possible in the information field 64 are reserved for non-standard
applications, 64 are reserved for internal network use and eight are defined by
ANSI/ETSI for diagnostic and loop-back functions. All remaining 120 free codes are
available for future standardization. For information about EOC channel commands and
programming refer to "Access to EOC of U-Interface", page 110.
Cyclic Redundancy Check Channel
The check digits (CRC bits CRC1, CRC2, …, CRC12) are transmitted at position M5 and
M6 in the U-superframe. This value is compared with the value calculated from the
previously received superframe. For more detailed functional information about the CRC
feature see "Cyclic Redundancy Check (CRC)", page 64.
Single Bits Channel
The Single Bits in the U-frame are defined to be bits M41 to M48 (eight bits) in addition
to the three bits M51, M52 and M61 and the bit FEBE. Bits M41 through M48 will be
referred to as M4 bits. The three bits M51, M52 and M61 will be referred to as "Additional
Overhead Bits". The single bits are used mainly to communicate status and maintenance
functions between the transceivers. The meaning of a bit position depends upon the
direction of transmission (upstream/downstream) and the operation mode (repeater or
NT/LT). For details about access to these bits, see "Access to the Single Bits of
U-Interface", page 115.
Semiconductor Group
69
Data Sheet 01.99