Xilinx RocketIO User Manual

RocketIO™ Transceiver User Guide www.xilinx.com 87
UG024 (v3.0) February 22, 2007
CRC (Cyclic Redundancy Check)
R
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:
As noted in Figure 2-25, pad bits are used to assure that the header, data, and CRC total
to the 64-byte minimum packet length. For packets that are already 64 bytes or longer, pad bits
are not used.
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:
• 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.
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 Figure 2-26.
Figure 2-25: Ethernet Mode
UG024_13_101602
Preamble
n Bytes
SOP SOF DATA R
0
R
1
R
2
R
3
Pad Bits EOP Trail Bits
2 to 3 Bytes
Figure 2-26: Infiniband Mode
UG024_14_020802
GRHLRHSOP
Global IBA
BTH
Packet
Payload
R
0
R
1
R
2
R
3
Variant CRC EOP
LRHSOP
Local IBA
BTH
Packet
Payload
R
0
R
1
R
2
R
3
Variant CRC EOP
Product Not Recommended for New Designs

Xilinx RocketIO Specifications

General

Brand	Xilinx
Model	RocketIO
Category	Transceiver
Language	English