DS589 Datasheet, PDF (2/6 Pages) Xilinx, Inc – Virtex-5 FPGA CRC Wizard v1.3

Virtex-5 FPGA CRC Wizard v1.3
Functional Overview
The CRC is an error checking mechanism for a block of data, such as a frame of network traffic. The
CRC Wizard allows the user to configure and use the CRC block in the Virtex-5 LXT/SXT/FXT device
using the LocalLink interface (Figure 1).
X-Ref Target - Figure 1
User
Logic
DATA_US[d-1:0]
REM_US[p:0]
SOF_N_US
EOF_N_US
SRC_RDY_N_US
DST_RDY_N_US
CRC
Block
DATA_DS[d-1:0]
REM_DS[p:0]
SOF_N_DS
EOF_N_DS
SRC_RDY_N_DS
DST_RDY_N_DS
Target
Protocol
Figure 1: CRC Block Example
DS589_01_082907
Application
The CRC Wizard calculates the CRC for packets of data from the user interface. The input of the CRC
Wizard can be 32-bits or 64-bits of data.
Functional Description
In Virtex-5 devices, each transceiver tile is paired with two CRC blocks. The CRC blocks can operate
independently as two 32-bit input CRC modules (CRC32), or can be combined into a single 64-bit input
CRC module (CRC64). The CRC modules use the standard 32-bit Ethernet polynomial for CRC
calculation. The CRC blocks are independent of the transceiver blocks.
The CRC Wizard generates two LocalLink compatible CRC modules, TX_CRC and RX_CRC, each
instantiating the Virtex-5 CRC block resource (see Figure 2, page 3.) The TX_CRC and RX_CRC
modules both have two LocalLink interfaces, upstream and downstream, allowing them to be inserted
into the transmit (TX_CRC) or receive (RX_CRC) path of the application design.
The TX_CRC module, Figure 3, page 3, generates a CRC value from data input on the upstream
interface. The module inserts the CRC byte(s) at the end of the frame on the downstream interface.
The RX_CRC module, Figure 4, page 3, calculates CRC on the incoming data from the upstream
interface while passing the data through to its downstream interface. The downstream interface
includes extra signals to indicate whether the incoming frame contains a valid CRC.
CRC_PASS_FAIL_N is generated by comparing the CRC calculated at the receive end with the CRC
obtained from the transmit end along with data.
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DS589 March 24, 2008
Product Specification