
DS33Z41 Quad IMUX Ethernet Mapper
8.16 Transmit Packet Processor
The Transmit Packet Processor accepts data from the Transmit FIFO performs bit reordering, FCS processing, packet error insertion, stuffing, packet abort sequence insertion,
Bit reordering changes the bit order of each byte. If bit reordering is disabled, the outgoing
FCS processing calculates an FCS and appends it to the packet. FCS calculation is a
Packet error insertion inserts errors into the FCS bytes. A single FCS bit is corrupted in each errored packet. The FCS bit corrupted is changed from errored packet to errored packet. Error insertion can be controlled by a register or by the manual error insertion input (LI.TMEI.TMEI). The error insertion initiation type (register or input) is programmable. If a register controls error insertion, the number and frequency of the errors are programmable. If FCS append is disabled, packet error insertion will not be performed. If packet processing is disabled, packet error insertion is not performed.
Stuffing inserts control data into the packet to prevent packet data from mimicking flags. A packet start indication is received, and stuffing is performed until, a packet end indication is received. Bit stuffing consists of inserting a zero directly following any five contiguous ones. If packet processing is disabled, stuffing is not performed.
There is at least one flag plus a programmable number of additional flags between packets. The
Packet abort insertion inserts a packet abort sequences as necessary. If a packet abort indication is detected, a packet abort sequence is inserted and
The packet scrambler is a x43 + 1 scrambler that scrambles the entire packet data stream. The packet scrambler runs continuously, and is never reset. In bit synchronous mode, scrambling is performed one bit at a time. In byte synchronous mode, scrambling is performed 8 bits at a time. Packet scrambling is programmable.
Once all packet processing has been completed serial data stream is passed on to the Transmit Serial Interface.
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