3.0 Circuit Descriptions
RS8953B/8953SPB
3.6 PRA Function
HDSL Channel Unit
3.6 PRA Function
This document specifies requirements for using the integrated service digital
network. Figure 3-27 shows an overview of the HDSL link between the
Termination Equipment (TE) and the Exchange Termination (ET).
Figure 3-27. An Overview of the PRA Transfer of Data
RS8953B
RSER
RS8953B
TSER
G
M
G
M
E-bits
G
RMSYNC
TMSYNC
HDSL
ET
E-bits
M
E-bits
G
E-bits
M
TE
TSER
RESER
TMSYNC
RMSYNC
NOTE(S): TE - Termination Equipment
ET - Exchange Termination
M - Monitor
ET - Exchange Termination
3.6.1 Transferring Data from HDSL to RSER
The following functions are available when transferring data from HDSL to
RSER: CRC4 monitoring, E-bit insertion, E-bits counter, and CRC4 generator.
When CRC4 monitoring is enabled, E1 data—which is received via
HDSL—is checked for error blocks by using the CRC4 procedure, as specified in
CCITT recommendation G.704[9], subclause 2.3.3. The check result, represented
in E-bits, is inserted into the data stream in the appropriate location.
When CRC4 monitoring is disabled, two options are available for E-bit
insertion: New values are inserted for the E-bits, or the E1 data stream remains
untouched. If new values are inserted, an external CPU must be used to program
the value of these bits. The E-bit insertion mode is repeated each E1 frame until
another value is programmed, or until another mode is selected.
The E-bits counter is continuously enabled and causes an 8-bit counter to
count the amount of E-bits reflected by the E1 stream. This information is
received via HDSL. This counter wraps around on full count. The value of the
counter needs to be accessible to an external CPU. The counter is reset upon
reading the value.
3-34
Conexant
N8953BDSB
CONEXANT [ CONEXANT SYSTEMS, INC ]
