Xilinx RocketIO User Manual

88 www.xilinx.com RocketIO™ Transceiver User Guide
UG024 (v3.0) February 22, 2007
Chapter 2: Digital Design Considerations
R
The CRC is calculated with certain bits masked in LRH and GRH, depending on whether
the packet is local or global. The size of these headers is shown in Table 2-21.
The CRC checks the LNH (Link Next Header) of the LRH. LRH is shown in Figure 2-27,
along with the bits the CRC uses to evaluate the next packet.
Note:
Minimum data length for this mode is defined by the protocol requirements.
Because of the complexity of the CRC algorithms and implementations, especially with
Infiniband, a more in-depth discussion is beyond the scope of this manual.
CRC_START_OF_PACKET,
CRC_END_OF_PACKET
When implementing USER_MODE CRC, Start of Packet (SOP) and End of Packet (EOP)
must be defined for the CRC logic. These delimiters must be one of the defined
K-characters (see Table B-2, page 143). These must be different than a clock correction
sequence (CCS) or IDLE sequence; otherwise, the CRC will mistake the CCS or IDLE for
SOP/EOP.
Note:
These attribute are not applicable to the other CRC formats.
RXCHECKINGCRC,
RXCRCERR
These two signals are status ports for the CRC circuitry.
RXCHECKINGCRC is asserted within several USRCLKs of the EOF being received from
RXDATA. This signals that the CRC circuitry has identified the SOF and the EOF.
If a CRC error occurred, RXCRCERR will be asserted at the same time that
RXCHECKINGCRC goes High.
Table 2-21: Global and Local Headers
Packet Description Size
LRH Local Routing Header 8 Bytes
GRH Global Routing Header 40 Bytes
BTH IBA Transport Header 12 Bytes
Figure 2-27: Local Route Header
UG024_15_020802
B
0
B1
7
− B1
0
B
2
B1
1
, B1
0
B
3
B
4
B
5
B
6
B
7
1 1 IBA Global Packet
1 0 IBA Local Packet
0 1 Raw Packet (CRC does not insert remainder)
0 0 Raw Packet (CRC does not insert remainder)
Product Not Recommended for New Designs

Xilinx RocketIO Specifications

General

Brand	Xilinx
Model	RocketIO
Category	Transceiver
Language	English