Xilinx RocketIO User Manual page 87

Product Not Recommended for New Designs
CRC (Cyclic Redundancy Check)
SOP Preamble
n Bytes
Designs should generate only the /K28.5/D16.2/ IDLE sequence for transmission, never
/K28.5/D5.6/. When the RocketIO CRC determines that the running disparity must be
inverted to satisfy Gigabit Ethernet requirements, it will convert the first /K28.5/D16.2/
IDLE following a packet to /K28.5/D5.6/, performing the necessary conversion.
Note that CRC generation for IDLE requires that the transmitted K28.5 be left-justified in
the MGT's internal two-byte data path. Observing the following restrictions assures
correct alignment of the packet delimiters:
•
•
•
INFINIBAND
The Infiniband CRC is the most complex mode, and is not supported in the CRC generator.
Infiniband CRC contains two computation types: an invariant 32-bit CRC, the same as in
Ethernet protocol; and a variant 16-bit CRC, which is not supported in the hard core.
Infiniband CRC must be implemented entirely in the FPGA fabric.
There are also two Infiniband Architecture (IBA) packets, a local and a global. Both of these
IBA packets are shown in
Local IBA
Global IBA
RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007
SOF DATA
Figure 2-25: Ethernet Mode
Note:
As noted in Figure
to the 64-byte minimum packet length. For packets that are already 64 bytes or longer, pad bits
are not used.
4-byte data path: K28.5 must appear in TXDATA[31:24] or TXDATA[15:8].
2-byte data path: K28.5 must appear in TXDATA[15:8].
1-byte data path: K28.5 must be strobed into the MGT on rising TXUSRCLK2 only
when TXUSRCLK is High.
Note:
Minimum data length for this mode is defined by the protocol requirements.
Note:
For correct operation of the Gigabit Ethernet CRC function, transmitted and received
frames must comply with the 802.3 specification regarding Gigabit Ethernet. This includes the
preamble maximum length.
Figure
Packet
SOP LRH BTH
Payload
SOP LRH GRH BTH
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Pad Bits R 0 R 1
2 to 3 Bytes
2-25, pad bits are used to assure that the header, data, and CRC total
2-26.
R R R
0 1 2
Packet
R
R
0 1
Payload
Figure 2-26: Infiniband Mode
R 2 R 3 EOP Trail Bits
UG024_13_101602
R
Variant CRC EOP
3
R R
Variant CRC
2 3
UG024_14_020802
R
EOP
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