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AR# 15337

AFX - Known Issues for Virtex-II AFX boards


This Answer Record describes the Known Issues for Virtex-II AFX boards.


1. The RESET button on certain AFX boards is not working correctly. To correct the problem, remove resistor R19 from the board.

2. Not all resistors shown on the schematics are present on the boards, as some are populated to enable or disable certain functionality. For example, on the FG676 board, the resistor pair R66/R14 is used to select either the output of the service FPGA or a test pad on the bottom of the board to drive the clock input of the Virtex-II FPGA. The board layout contains only three solder pads for these resistors, allowing only one location to be populated.

3. The "demo.v" file that comes with the AFX board contains a syntax error. This problem is discussed in (Xilinx Answer 14574).

4. On the FG456 board, when the mode switch is set to include the user PROM, the PROM cannot consistently be found in the JTAG chain.

A service FPGA configuration problem exists with respect to the PROM's RESET_OE pin. When this pin is held High, the PROM will be in a state such that it cannot be found in the chain and therefore cannot be programmed . When the tools attempt to detect the PROM in the JTAG chain, the service FPGA sometimes weakly drives the RESET_OE pin High. However, this pin should be High when the PROM is configuring the FPGA.

To successfully find and program the PROM:

a. Connect the configuration jumpers as usual to the CONFIGURATION PORT USER PROM AND FPGA header, and set up the mode switches in the normal JTAG manner as if there were no problem finding or programming the PROM.

b. Ground the RESET_OE pin (which is found on the PROM DAUGHTER CARD INTERFACE) by connecting it to the GND pin on the JTAG INTERFACE SERVICE PROM AND FPGA header. This will allow the PROM to be found in the JTAG chain.

c. Power up the board and follow the usual steps for programming the PROM.

IMPORTANT: Before using the PROM to configure the FPGA:

d. Un-ground the RESET_OE pin. If this is not done, the PROM will not be able to configure the FPGA.

e. Use the PROM to configure the FPGA as usual.

The "demo.bit" file designed to target a XC2V80 device in the HW-AFX-FG256-200 board actually targets a XC2V250 device.

AR# 15337
Date Created 09/03/2007
Last Updated 12/15/2012
Status Active
Type General Article