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AR# 11208

Virtex-II - How do I use the VRP/VRN and ALT_VRN/ALT_VRP pins?


Keywords: DCI, SelectMAP, data, configuration, XCITE, 5.1i

In the Virtex-II package pin-out table, Banks 4 and 5 contain two sets of VRN/VRP pins:

- One set is labeled "VRP/VRN"
- One set is labeled "ALT_VRP/ALT_VRN"

For all new designs, the VRP/VRN pins should be used.

The ALT_VRP/ALT_VRN pins in Banks 4 and 5 are shared with the SelectMAP configuration data pins. When necessary, the ALT_VRP/ALT_VRN pins can be used as described below. However, ALT_VRP/ALT_VRN pins should not be used in ES devices.

For a CS144 package or XC2V40 and XC2V80, only the ALT_VRP/ALT_VRN pins are available in Banks 4 and 5. (The VRP/VRN are not available.) Consequently, if a DCI I/O is required in Bank 4 or 5 for these devices, you must use ALT_VRN/ALT_VRP.



To use ALT_VRP/ALT_VRN, follow these steps:
1. Set the XIL_VIRTEX2_PKG_USEALT environment variable:
- PC Platform: set XIL_VIRTEX2_PKG_USEALT=1
- UNIX Workstation: setenv XIL_VIRTEX2_PKG_USEALT 1
2. Set the BitGen option "Match_cycle:NoWait."
3. Wait for approximately 750 us after configuration before using the DCI I/O. This is necessary because ALT_VRP/ALT_VRN are activated after configuration is finished. This extra time allows DCI to complete its impedance-matching before the I/Os are used.

NOTE: The "FreezeDCI" BitGen option cannot be used when ALT_VRP/ALT_VRN pins are used. Please see (Xilinx Answer 13012) for details.

Beginning in 5.1i Service Pack 2, if your design uses DCI in Bank 4 or 5, the software automatically uses the ALT_VRN/ALT_VRP pins for designs targeting 2V40 or 2V80 devices. This does not happen automatically for 2V250 CS144 packages. If you use the 2V250 CS144 package, please perform Steps 1 and 2 above.


Additional Notes for Older Software Versions
1. If you are using the 4.1i software, please follow the steps above.
2. In 3.1i Service Pack 8, only the new VRP/VRN pair is available in Banks 4 and 5. If you want to access the ALT_VRP/ALT_VRN (the alternate pair), you must use the older package file. To use the older package in 3.1i Service Pack 8, please download the following file:
AR# 11208
Date 04/12/2006
Status Archive
Type ??????