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S/UNI-ATLAS-3200 Telecom Standard Product Data Sheet
Preliminary
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-1990553, Issue 4
345
HEC
The HEC bit is used to indicate whether the HEC/UDF word is included in ATM cells. When
the value is ‘1’, the ATM cells contain the HEC/UDF word. When the value is ‘0’, the ATM
cells do not contain the HEC/UDF word. In any event, the HEC is undefined at the ATM
layer, and will not be calculated by RxLink. This bit cannot be changed during operation and
can only be changed when RXLRST is logic one.
USE_STPA
The USE_STPA bit is used to indicate whether the TxLink will recognize transitions on the
TLP_STPA pin. When USE_STPA is logic 0, TLP_STPA is ignored and transfers are based
solely on TLP_PTPA. If USE_STPA is logic 1, then on sampling STPA high, the TxLink will
immediately cease transferring data. The TLP_STPA signal is valid 3 clocks after TSX is
driven on the interface by the LINK device; TxLink stops transmitting data three cycles after
PRELEN[1:0]
The PRELEN bits are used to indicate the size of the prepend applied to the ATM cells to
external blocks. A value of ‘00’ indicates no prepend word. A value of ‘01’ indicates 1
prepend word. A value of ‘10’ indicates 2 prepend words A value of ‘11’ is invalid. These bits
cannot be changed during operation and can only be changed when RXPRST is logic one.
These bits apply to all PHY channels. The sum of PRELEN + POSTLEN must not exceed 2,
or correct operation is not guaranteed
.
POSTLEN[1:0]
The POSTLEN bits are used to indicate the size of the postpend applied to the ATM cells. A
value of ‘00’ indicates no postpend word. A value of ‘01’ indicates 1 postpend word. A value
of ‘10’ indicates 2 postpend words. A value of ‘11’ is invalid. These bits cannot be changed
during operation and can only be changed when RXPRST is logic one. These bits apply to all
PHY channels. The sum of PRELEN + POSTLEN must not exceed 2, or correct operation is
not guaranteed
.