
IDT82P2281
SINGLE T1/E1/J1 LONG HAUL / SHORT HAUL TRANSCEIVER
Functional Description
58
August 20, 2009
3.12
BIT-ORIENTED MESSAGE RECEIVER
The Bit-Oriented Message (BOM) can only be received in the ESF
format in T1/J1 mode.
The BOM pattern is ‘111111110XXXXXX0’ which occupies the DL of
the F-bit in the ESF format (refer to
Table 13). The six ‘X’s represent the
message. The BOM is declared only when the pattern is matched and
the received message is identical 4 out of 5 consecutive times or 8 out of
10 consecutive times and differs from the previous message. The identi-
fication time is selected by the AVC bit. After a new BOM is declared, the
message is loaded into the BOC[5:0] bits. Every time when the BOC[5:0]
bits are updated, it will be indicated by the BOCI bit. A ‘1’ in the BOCI bit
means there is an interrupt. The interrupt will be reported by the INT pin
if the BOCE bit is ‘1’.
In BITS application, network timing recovery is required. In addition
to timing recovery, the incoming line can carry Synchronization Status
Messages, or SSM, to indicate the quality level of the incoming clock.
SSM (in code words) are transmitted and/or received through the data
link bits (DS1 ESF formats) in T1/J1 mode. XBOC[5:0] and BOC[5:0]
mode can be used to transmit and receive the code words of SSM,
respectively. In E1 mode, Sa bits in Time Slot 0 can be used for transmit
or receive SSM code words.
In T1/J1 ESF mode, the BOC[5:0] bits can be used to hold the
received codeword in SSM application. The XBOC[5:0] bits, on the other
hand, can be used to transmit the SSM codeword to the network far end.
In E1 mode, each of the Sa[4:8] bits can be used for the same pur-
pose. For example, if the Sa[4] bit is used in transmit direction, SSM is
transmitted by using the Sa[4] bit; in receive direction, the E1 Sa4 Code-
word Register contains the received SSM codeword.
3.13
INBAND LOOPBACK CODE DETECTOR (T1/J1
ONLY)
The Inband Loopback Code Detector tracks the loopback activate/
deactivate codes only in framed or unframed T1/J1 data stream, and
meets ANSI T1.403 9.3.1.
The received data stream is compared with the target activate/
deactivate code whose length and content are programmed in the
ASEL[1:0]/DSEL[1:0] bits and the ACT[7:0]/DACT[7:0] bits respectively.
In framed mode, the F-bit is selected by the IBCDIDLE bit to compare
with the target activate/deactivate code or not. In unframed mode, all
193 bits are compared with the target activate/deactivate code.
After four consecutive correct activate/deactivate codes are found
in the received data stream, the Inband Loopback Code Detector keeps
on monitoring the bit error, i.e., the bit differs from the target activate/
deactivate code. If in more than 126 consecutive 39.8ms fixed periods,
less than 600 bit errors are detected in each 39.8ms, the activate/deacti-
vate code is detected and the corresponding LBA/LBD bit will indicate it.
Once more than 600 bit errors are detected in a 39.8ms fixed period, the
activate/deactivate code is out of synchronization and the corresponding
LBA/LBD bit will be cleared. However, even if the F-bit is compared,
whether it is matched or not, the result will not cause bit errors, that is,
the comparison result of the F-bit is discarded.
Any transition (from ‘0’ to ‘1’ or from ‘1’ to ‘0’) on the LBA/LBD bit
will set the LBAI/LBDI bit, which means there is an interrupt. The inter-
rupt will be reported by the INT pin if the corresponding LBAE/LBDE bit
is set to ‘1’.
Bit
Register
T1/J1 Address (Hex)
AVC
BOC Control
081
BOCE
BOC[5:0]
RBOC Code
083
BOCI
BOC Interrupt Indication
082
XBOC[5:0]
T1/J1 XBOC Code
080
Sa[4:8]
E1 TS0 International / National
054
Sa4[1:4]
E1 Sa4 Codeword
056
Bit
Register
T1/J1 Address (Hex)
ASEL[1:0]
IBCD Detector Configuration
076
DSEL[1:0]
IBCDIDLE
ACT[7:0]
IBCD Activate Code
078
DACT[7:0]
IBCD Deactivate Code
079
LBA
IBCD Detector Status
077
LBD
LBAI
IBCD Interrupt Indication
07B
LBDI
LBAE
IBCD Interrupt Control
07A
LBDE