XRT79L71 Datasheet, PDF (260/441 Pages) Exar Corporation – 1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC

XRT79L71
REV. P1.0.3
BIT NUMBER
NAME
2
Uncorrectable HEC Byte
Discard
1
COSET Polynomial Addi-
tion
0
Regenerate HEC Byte
Enable
PRELIMINARY
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1 - CHANNEL DS3/E3 ATM UNI/PPP COMBO IC
TYPE
R/W
R/W
R/W
DESCRIPTION
Uncorrectable HEC Byte Discard:
This READ/WRITE bit-field permits the user to configure the
Receive ATM Cell Processor block to either automatically dis-
card all incoming ATM cells that contain "uncorrectable" HEC
byte errors.
If the user implements this feature, then the Receive ATM Cell
Processor block will automatically discard any cells that fit into
any one of the following categories.
• ATM cells that contain multi-bit HEC byte errors.
• ATM cells that contain single-bit HEC byte errors, while the
Receive ATM Cell Processor block is operating in the
"Detection Mode".
If the user does NOT implement this feature, then the Receive
ATM Cell Processor block will NOT discard any cells that fit into
any one of the above-mentioned categories. These cells (along
with un-erred or cells with "correctable" HEC byte errors) will be
retains for further processing.
0 - Configures the Receive ATM Cell Processor block to retain
ALL ATM cells (even those with "uncorrectable" HEC byte errors)
for further processing.
1 - Configures the Receive ATM Cell Processor block to auto-
matically discard all incoming ATM cells that contain "uncorrect-
able" HEC byte errors. All remaining cells will be retained for
further processing.
COSET Polynomial Addition:
This READ/WRITE bit-field permits the user to configure the
Receive ATM Cell Processor block to account for the fact that the
HEC bytes (within the incoming ATM cell traffic) also include the
Modulo-2 addition of the Coset Polynomial (e.g., x^6 + x^4 + x^2
+ 1), when performing HEC Byte Verification.
0 - Configures the Receive ATM Cell Processor block to NOT
account for the Coset Polynomial within the HEC bytes of the
incoming ATM cells.
1 - Configures the Receive ATM Cell Processor block to account
for the Coset Polynomial within the HEC bytes of the incoming
ATM cells.
Regenerate HEC Byte Enable:
This READ/WRITE bit-field permits the user to configure the
Receive ATM Cell Processor block to automatically re-compute
and insert a new HEC byte into each incoming ATM cell that con-
tains an uncorrectable HEC byte.
0 - Does not configure the Receive ATM Cell Processor block to
compute and insert a new HEC byte into ATM cells that contains
an "uncorrectable" HEC byte error.
1 - Configures the Receive ATM Cell Processor block to compute
and insert a new HEC byte into any incoming ATM cell that con-
tains an "uncorrectable" HEC byte error.
NOTE: If the user wishes to implement this feature, then he/she
must disable the "Uncorrectable HEC Byte Discard"
feature, by setting Bit 2 (Uncorrectable HEC Byte
Discard) within this register, to "0".
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