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generated by inserting an HDB3 signature into the bipolar data stream if both the POS and NEG signals are zero

for four consecutive clock periods. Zero suppression encoding can be disabled which will result in AMI-coded data.

Error insertion is also performed. Error insertion inserts bipolar violation (BPV) or excessive zero (EXZ) errors onto

the bipolar signal. A BPV error will be inserted when three consecutive ones occur. An EXZ error will be inserted

when three (or four) consecutive zeros on the bipolar signal occur by inhibiting the insertion of a B3ZS (HDB3)

signature. There will be at least one intervening pulse between consecutive BPV or EXZ errors. A single BPV or

EXZ error inserted will be detected as a single BPV/EXZ error at the far-end, and will not cause any other type of

error to be detected. For example, if a BPV error is inserted, the far-end should not also detect a data error.

10.10.4 Transmit Line Interface

The Transmit Line Interface accepts a bipolar data stream from the B3ZS/HDB3 Encoder, performs error insertion,

and transmits the bipolar data stream.

Error insertion inserts BPV or EXZ errors into the bipolar signal. When a BPV error is to be inserted, the Transmit

Line Interface waits for the next occurrence of three consecutive ones. The first bipolar one is generated according

to the normal AMI rules. The second bipolar one is generated by transmitting the same values on TPOS and TNEG

as the values for the first one. The third bipolar one is generated according to the normal AMI rules. When an EXZ

error is to be inserted, the Transmit Line Interface waits for the next occurrence of three (four) consecutive zeros on

the bipolar signal, and inhibits the insertion of a B3ZS (HDB3) signature. There must be at least one intervening

one between consecutive BPV or EXZ errors. A single BPV or EXZ error inserted must be detected as a single

BPV/EXZ error at the far-end, and not cause any other type of error to be detected. For example, if a BPV error is

inserted, the far-end should not also detect a data error. If a second error insertion request of a given type (BPV or

EXZ) is initiated before a previous request has been completed, the second request will be ignored.

The outgoing bipolar data stream consists of positive pulse data (TPOSn) and negative pulse data (TNEGn).

TPOSn and TNEGn are updated on the rising edge of TLCLKn.

10.10.5 Receive Line Interface

The Receive Line Interface receives a bipolar signal. The incoming bipolar data line consists of positive pulse data

(RPOSn), negative pulse data (RNEGn), and clock (RLCLKn) signals. RPOSn and RNEGn are sampled on the

rising edge of RLCLKn. The incoming bipolar signal is checked for a Loss Of Signal (LOS) condition, and passed

on to B3ZS/HDB3 Decoder. An LOS condition is declared if both RPOSn and RNEGn do not have any transitions

for 192 clock cycles. The LOS condition is terminated after 192 clock cycles without any EXZ errors. Note: When

zero suppression (B3ZS or HDB3) decoding is disabled, the LOS condition is cleared, and cannot be detected.

10.10.6 B3ZS/HDB3 Decoder

The B3ZS/HDB3 Decoder receives a bipolar signal from the LIU (or the RPOS/RNEG pins). The incoming bipolar

signal is checked for a Loss of Signal (LOS) condition. An LOS condition is declared if both the positive pulse data

and negative pulse data signals do not have any transitions for 192 clock cycles. The LOS condition is terminated

after 192 clock cycles without any EXZ errors.

B3ZS/HDB3 Decoder performs EXZ detection, zero suppression decoding, BPV detection, and bipolar to unipolar

conversion.

EXZ detection checks the bipolar data stream for excessive zeros (EXZ) errors. In B3ZS mode, an EXZ error is

declared whenever there is an occurrence of 3 or more zeros. In HDB3 mode, an EXZ error is declared whenever

there is an occurrence of 4 or more zeros. EXZ errors are accumulated in the EXZ counter (LINE.REXZCR

Zero suppression decoding converts B3ZS or HDB3 encoded bipolar data into an AMI bipolar signal. In B3ZS

mode, the encoded bipolar signal is checked for a B3ZS signature. If a B3ZS signature is found, it is replaced with

three zeros. In HDB3 mode, the encoded bipolar signal is checked for an HDB3 signature. If an HDB3 signature is

found, it is replaced with four zeros. The format of both an HDB3 signature and a B3ZS signature is programmable.

When LINE.RCR.REZSF = 0, the decoder will search for a zero followed by a BPV in B3ZS mode, and in HDB3

mode it will search for two zeros followed by a BPV. If LINE.RCR.REZSF = 1, the same criteria is applied with an

additional requirement that the BPV must be the opposite polarity of the previous BPV. See Figure 10-26 and

Figure 10-27. Zero suppression decoding is also programmable (on or off). Note: Immediately after a reset or a

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