DS3172 Maxim Integrated, DS3172 Datasheet - Page 93

• Manufacturer Part Number: DS3172
• Description: Network Controller & Processor ICs Dual DS3/E3 Single Chip Transceiver
• Manufacturer: Maxim Integrated

Specifications of DS3172

• Part # Aliases: 90-31720-000

DS3171/DS3172/DS3173/DS3174
FA1 and FA2 bytes respectively). Framing error(s) can be inserted one error at a time, or four consecutive frames.
The framing error insertion mode (single or four) is programmable.
The type of BIP-8 error(s) inserted is programmable (errored BIP-8 bit, or errored BIP-8 byte). An errored BIP-8 bit
is inverting a single bit error in the EM byte. An errored BIP-8 byte is inverting all eight bits in the EM byte. BIP-8
error(s) can be inserted one error at a time, or continuously. The BIP-8 error insertion mode (single or continuous)
is programmable.
An REI error is generated by forcing the second bit of the MA byte to a one. REI error(s) can be inserted one error
at a time, or continuously. The REI error insertion mode (single or continuous) is programmable.
Each error type (framing, BIP-8, or REI) has a separate enable. Continuous error insertion mode inserts errors at
every opportunity. Single error insertion mode inserts an error at the next opportunity when requested. The framing
multi-error insertion mode inserts the indicated number of errors at the next opportunities when requested. i.e., a
single request will cause multiple errors to be inserted. The requests can be initiated by a register bit(TSEI) or by
the manual error insertion input (TMEI). The error insertion request source (register or input) is programmable. The
insertion of each particular error type is individually enabled. Once all error insertion has been performed, the data
stream is passed on to overhead insertion.
10.6.8.4 Transmit G.832 E3 Overhead Insertion
Overhead insertion can insert any (or all) of the E3 overhead bytes into the E3 frame. The E3 overhead bytes FA1,
FA2, EM, TR, MA, NR, and GC can be sourced from the transmit overhead interface (TOHCLK, TOH, TOHEN, and
TOHSOF). The EM byte is sourced as an error mask (modulo 2 addition of the input EM byte and the generated
EM byte). The E3 overhead insertion is fully controlled by the transmit overhead interface. If the transmit overhead
data enable signal (TOHEN) is driven high, then the bit on the transmit overhead signal (TOH) is inserted into the
output data stream. Insertion of bits using the TOH signal overwrites internal overhead insertion.
10.6.8.5 Transmit G.832 E3 AIS Generation
G.832 E3 AIS generation overwrites the data stream with AIS. If transmit AIS is enabled, the data stream (payload
and E3 overhead) is forced to all ones.
10.6.8.6 Receive G.832 E3 Frame Processor
The G.832 E3 frame format is shown in
Figure
10-18. FA1 and FA2 are the Frame Alignment bytes. EM is the Error
Monitoring byte used for path error monitoring. TR is the Trail Trace byte used for end-to-end connectivity
verification. MA is the Maintenance and Adaptation byte used for far-end path status and performance monitoring
(See
Figure
10-19). NR is the Network Operator byte allocated for network operator maintenance purposes. GC is
the General-Purpose Communications Channel byte allocated for user communications purposes.
10.6.8.7 Receive G.832 E3 Framing
G.832 E3 framing determines the G.832 E3 frame boundary. The frame boundary is found by identifying the frame
alignment bytes FA1 and FA2, which have a value of F6h and 28h respectively. The framer is an off-line framer
that updates the data path frame counters when an out of frame (OOF) condition has been detected. The use of an
off-line framer reduces the average time required to reframe, and reduces data loss caused by burst error. The
G.832 E3 framer checks each bit position for the frame alignment word (FA1 and FA2). The frame boundary is set
once the frame alignment word is identified. Since, the frame alignment word check is performed one bit at a time,
up to 4296 checks may be needed to find the frame boundary. The data path frame counters are updated if an
error free frame alignment word is received for two additional frames, and an OOF condition is present.
10.6.8.8 Receive G.832 E3 Performance Monitoring
Performance monitoring checks the E3 frame for alarm conditions and errors. The alarm conditions detected are
OOF, LOF, COFA, LOS, AIS, RUA1, and RDI. The errors accumulated are framing, parity, and Remote Error
Indication (REI) errors. An Out Of Frame (OOF) condition is declared when four consecutive frame alignment
words (FA1 and FA2) contain one or more errors, when 986 or more frames out of 1,000 frames has a BIP-8 block
error, or at the next framing word check when a manual reframe is requested. An OOF condition is terminated
when three consecutive frame alignment words (FA1 and FA2) are error free or the G.832 E3 framer updates the
data path frame counters.
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