IDT82P2828
28(+1) CHANNEL HIGH-DENSITY T1/E1/J1 LINE INTERFACE UNIT
Functional Description
49
February 6, 2009
3.5.5.2 Pattern Detection
Data received from the line side or data input from the transmit
system side may be extracted for pattern detection. The direction of data
extraction is determined by the PD_POS bit (b3,
PD,...). One of PRBS or
ARB pattern is selected for detection and IB detection is always active.
If data is extracted from the receive path, before pattern detection the
data should be decoded by using AMI or B8ZS (for T1/J1) / HDB3 (for
E1). The decoding rule is selected by the R_CODE bit (b2,
RCF1,...).If data is extracted from the transmit path, before pattern detection
the data should be decoded by using AMI or B8ZS (for T1/J1) / HDB3
(for E1) in Transmit Dual Rail NRZ Format mode and Transmit Dual Rail
RZ Format mode. The decoding rule is selected by the T_CODE bit (b2,
Pseudo Random Bit Sequence (PRBS) /Arbitrary Pattern (ARB)
Detection
The extracted data can be optionally inverted by the PAD_INV bit
(b2,
PD,...) before PRBS/ARB detection.
The extracted data is used to compare with the desired pattern. The
desired pattern is re-generated from the extracted data if the desired
pattern is (2^20 - 1) QRSS per O.150-4.5, (2^15 - 1) PRBS per O.152 or
(2^11 - 1) PRBS per O.150; or the desired pattern is programmed in the
ARB. The desired pattern is selected by the PAD_SEL[1:0] bits (b1~0,
In summary, do the followings step by step to detect PRBS/ARB:
Select the detection direction by the PD_POS bit (b3,
PD,...);
pattern is desired - this step is omitted if the PRBS pattern is
desired;
Select the desired PRBS/ARB pattern by the PAD_SEL[1:0] bits
The priority of decoding, data inversion, pattern re-generation, bit
programming and pattern comparison is shown in
Figure-28.Figure-28 PRBS / ARB Detection
During comparison, if the extracted data coincides with the re-gener-
ated PRBS pattern or the programmed ARB pattern for more than 64-bit
hopping window, the pattern is synchronized and the PA_S bit (b5,
In synchronization state, if more than 6 PRBS/ARB errors are
detected in a 64-bit hopping window, the pattern is out of synchroniza-
tion and the PA_S bit (b5,
STAT1,...) will be cleared.
In synchronization state, each mismatched bit will generate a PRBS/
ARB error. When a PRBS/ARB error is detected during the synchroniza-
tion, the ERR_IS bit (b1,
INTS2,...) will be set and an interrupt will be
reported by INT if not masked by the ERR_IM bit (b1,
INTM2,...). The
PRBS/ARB error may be counted by an internal Error Counter. Refer to
A transition from ‘0’ to ‘1’ on the PA_S bit (b5,
STAT1,...) or any tran-
sition (from ‘0’ to ‘1’ or from ‘1’ to ‘0’) on the PA_S bit (b5,
STAT1,...) will
set the PA_IS bit (b5,
INTS1,...) to ‘1’, as selected by the PA_IES bit (b5,
reported by INT if not masked by the PA_IM bit (b5,
INTM1,...).The PRBS/ARB synchronization status may be indicated by the
from Rx path
or Tx path
Decoding
Data
Inversion
PRBS Re-
Generation
Comparison
ARB[23:0]
Programming