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DS33R11 Ethernet Mapper with Integrated T1/E1/J1 Transceiver
67 of 344
Bit reordering changes the bit order of each byte. If bit reordering is disabled, the incoming 8-bit data stream
DT[1:8] with DT[1] being the MSB and DT[8] being the LSB is output to the Receive FIFO with the MSB in RFD[7]
(or 15, 23, or 31) and the LSB in RFD[0] (or 8, 16, or 24) of the receive FIFO data RFD[7:0] (or 15:8, 23:16, or
31:24). If bit reordering is enabled, the incoming 8-bit data stream DT[1:8] is output to the Receive FIFO with the
MSB in RFD[0] and the LSB in RFD[7] of the receive FIFO data RFD[7:0]. DT[1] is the first bit received from the
incoming data stream.
Once all of the packet processing has been completed, The 8-bit parallel data stream is demultiplexed into a 32-bit
parallel data stream. The Receive FIFO data is passed on to the Receive FIFO with packet start, packet end,
packet abort, and modulus indications. At a packet end, the 32-bit word may contain 1, 2, 3, or 4 bytes of data
depending on the number of bytes in the packet. The modulus indications indicate the number of bytes in the last
data word of the packet.
Figure 9-11. HDLC Encapsulation of MAC Frame
Flag(0x7E)
Destination Adrs(DA)
Source Adrs(SA)
Length/Type
Number of Bytes
1
6
6
2
MAC Client Data
46-1500
PAD
FCS for MAC
4
FCS for HDLC
Flag(0x7E)
0 / 2 / 4
MSB LSB