LXT351 datasheet(21/46 Pages) INTEL

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T1/E1 Short Haul Transceiver with Crystal-less Jitter Attenuation — LXT351

Datasheet

2.5.3

Error Insertion and Detection

2.5.3.1

Bipolar Violation Insertion (INSBPV)

Bipolar violation insertion is available In Unipolar mode. Choosing Unipolar mode configures the

INSBPV pin. To insert bipolar violation (BPV), a Low-to-High transition on the INSBPV is

required. Sampling occurs on the falling edge of TCLK. When INSBPV goes High a BPV is

inserted on the next available mark except in the four following situations:

• Zero suppression (HDB3 or B8ZS) is not violated

• If LLOOP and TAOS are both active, the BPV is looped back to RNEG/BPV indicator and the

line driver transmits all ones with no violation

• BPV insertion is disabled with RLOOP active

With the LXT351 configured to transmit internally generated data patterns, a BPV can be inserted

into the transmit pattern regardless of whether the device is in the Unipolar or Bipolar mode of

operation.

2.5.3.2

Logic Error Insertion (INSLER)

When configured to transmit internally generated data patterns, a logic error is inserted into the

transmit data pattern when the INSLER pin transitions Low-to-High. Note that in QRSS mode,

there is no logic error insertion on a jammed bit (i.e., a bit forced to one to suppress transmission of

more than 14 consecutive zeros). The transceiver routes data patterns the same way it routes data

applied to TPOS/TNEG. Therefore, the inserted logic error will follow the data flow path of the

active loopback mode.

2.5.3.3

Bipolar Violation Detection (BPV)

When the internal encoders/decoders are disabled or when configured in Unipolar mode, bipolar

violations are reported at the BPV pin. BPV goes High for a full clock cycle to indicate receipt of a

BPV. When the encoders/decoders are enabled, the LXT351 does not report bipolar violations due

to the line coding scheme.

2.5.3.4

HDB3 Code Violation Detection (CODEV)

An HDB3 code violation (CODEV) occurs when two consecutive bipolar violations of the same

polarity are received (refer to ITU O.161). When CODEV detection is enabled, the BPV pin goes

High for a full RCLK cycle to report a CODEV violation. Note that bipolar violations and zero

substitution violations will also be reported on the BPV pin if these options are enabled.

HDB3 code violation detection is enabled when the HDB3 encoders/decoders are enabled. This

requires that CR1.ENCENB = 1, also CR1.EC3:1 = 000, which establishes E1 operation. To select

CODEV detection, set bit CR4.CODEV = 1.

2.5.3.5

HDB3 Zero Substitution Violation Detection (ZEROV)

An HDB3 ZEROV is the receipt of four or more consecutive zeros. This does not occur with

correctly encoded HDB3 data unless there are transmission errors. The BPV pin goes High for a

full RCLK cycle to report a ZEROV. Note that when ZEROV detection enabled, the BPV pin will

also indicate received BPVs and CODEVs, if these detection options are enabled.

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