S/UNI®-JET Data Sheet
Released
10.16 XBOC Bit Oriented Code Generator
The Bit Oriented Code Generator (XBOC) Block transmits 63 of the possible 64 bit oriented
codes (BOC) in the C-bit parity FEAC channel. A BOC is a 16-bit sequence consisting of eight
ones, a zero, six code bits, and a trailing zero (111111110xxxxxx0) which is repeated as long as
the code is not 111111.
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The code to be transmitted is programmed by writing the XBOC Code Register. The 64 code
(111111) is similar to the HDLC idle sequence and is used to disable the transmission of any bit
oriented codes. When transmission is disabled, the FEAC channel is set to all ones.
10.17 TDPR PMDL Transmitter
The Path Maintenance Data Link Transmitter (TDPR) provides a serial data link for the C-bit
parity PMDLin DS3, the serial Network Operator byte or the General Purpose datalink in G.832
E3, the National Use bit datalink in G.751 E3, or the m-bit datalink in J2. The TDPR is used
under microprocessor control to transmit HDLC data frames. It performs all of the data
serialization, CRC generation, zero-bit stuffing, as well as flag, and abort sequence insertion.
Upon completion of the message, a CRC-CCITT FCS can be appended, followed by flags. If the
TDPR transmit data FIFO underflows, an abort sequence is automatically transmitted.
When enabled, the TDPR continuously transmits flags (01111110) until data is ready to be
transmitted. Data bytes to be transmitted are written into the TDPR Transmit Data Register. The
TDPR automatically begins transmission of data once at least one complete packet is written into
its FIFO. All complete packets of data will be transmitted if no error condition occurs. After the
last data byte of a packet, the CRC FCS (if CRC insertion has been enabled) and a flag, or just a
flag (if CRC insertion has not been enabled) is transmitted. The TDPR then returns to the
transmission of flag characters until the next packet is available for transmission. The TDPR will
also force transmission of the FIFO data once the FIFO depth has surpassed the programmable
upper limit threshold.
Transmission commences regardless of whether or not a packet has been completely written into
the FIFO. The user must be careful to avoid overfilling the FIFO. Underruns can only occur if the
packet length is greater than the programmed upper limit threshold because, in such a case,
transmission will begin before a complete packet is stored in the FIFO.
An interrupt can be generated once the FIFO depth has fallen below a user-configured lower
threshold as an indicator for the user to write more data. Interrupts can also be generated if the
FIFO underflows while transmitting a packet when the FIFO is full, or if the FIFO is overrun.
If there are more than five consecutive ones in the raw transmit data or in the CRC data, a zero is
stuffed into the serial data output. This prevents the unintentional transmission of flag or abort
sequences.
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-1990267, Issue 3
72
PMC [ PMC-SIERRA, INC ]
