XRT83SL34 datasheet(27/80 Pages) EXAR

27 / 80 page

XRT83SL34

QUAD T1/E1/J1 SH TRANSCEIVER WITH CLOCK RECOVERY AND JITTER ATTENUATOR

PRELIMINARY

REV. P1.0.8

TRANSMIT HDB3/B8ZS ENCODER

The Encoder function is available in both Hardware and Host modes on a per channel basis by controlling the

TNEG_n/CODES_n pin or CODES interface bit. The encoder is only available in single-rail mode. In E1 mode

and with HDB3 encoding selected, any sequence with four or more consecutive zeros in the input serial data

from TPOS_n/TDATA_n, will be removed and replaced with 000V or B00V, where “B” indicates a pulse

conforming with the bipolar rule and “V” representing a pulse violating the rule. An example of HDB3 Encoding

is shown in Table 3. In a T1 system, an input data sequence with eight or more consecutive zeros will be

removed and replaced using the B8ZS encoding rule. An example of Bipolar with 8 Zero Substitution (B8ZS)

encoding scheme is shown in Table 4. Writing a “1” into the CODES_n interface bit or connecting the TNEG_n/

CODES_n pin to a “High” level selects the AMI coding for both E1 or T1 systems.

FIGURE 10. TRANSMIT CLOCK AND INPUT DATA TIMING

TABLE 3: EXAMPLES OF HDB3 ENCODING

NUMBER OF PULSE BEFORE NEXT 4 ZEROS

NEXT 4 BITS

Input

0000

HDB3 (case1)

odd

000V

HDB3 (case2)

even

B00V

TABLE 4: EXAMPLES OF B8ZS ENCODING

CASE 1PRECEDING PULSE

NEXT 8 BITS

Input

00000000

B8ZS

000VB0VB

AMI Output

000+ -0- +

CASE 2

Input

00000000

B8ZS

000VB0VB

AMI Output

000- +0+ -

TCLK

TPOS/TDATA

TNEG

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