3.0 Circuit Descriptions
RS8953B/8953SPB
3.6 PRA Function
HDSL Channel Unit
If CRC4 monitoring is disabled, new values must be inserted into the E-bits, or
the E-bits must pass transparently (from the input TSER). If new values are
inserted, these bits are obtained by enabling an external CPU to program a 2-bit
register.
The E-bits counter is continuously enabled and causes an 8-bit counter to
count the amount of E-bits errors. It wraps around on full count. An external CPU
must be available to read the value of the counter. The counter is reset upon
reading the value.
The CRC4 generator, when enabled, causes the E1 data (TSER) to be fed into
a CRC4 generator. The CRC bits are inserted into the correct location of the data
stream (TSER) according to the CRC4 procedure which is specified in CCITT
recommendation G.704.
If the CRC4 generator is disabled, new values can be inserted for the CRC4
bits, or the CRC4 bits can be passed transparently (from the input TSER). If new
values are inserted, the new value is stored in a 4-bits register and is repeatedly
inserted into the correct location of the data stream. This insertion process is
continuously repeated until a new mode is selected.
3.6.5 Inserting Data Transferred from TSER to HDSL
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Each A-bit and SA4, SA5, SA7, and SA8 bit may be selected as
transparent or non-transparent. For non-transparent bits, the new value of
the certain bit is stored in a register and is inserted into the correct location
of the data stream (TSER).
The SA6 bits may be transferred either transparently or non-transparently.
Selecting transparent or non-transparent affects all four SA6 bits. For
non-transparent transfers, the new value of the bits is stored in a register
and is inserted into the correct location of the data stream (TSER).
The FAS bits may be transferred either transparently or non-transparently.
Selecting transparent or non-transparent affects all the FAS bits. For
non-transparent bits, the FAS value is inserted into the correct location of
the data stream (TSER). The FAS is a constant pattern.
3-36
Conexant
N8953BDSB
CONEXANT [ CONEXANT SYSTEMS, INC ]
