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AR# 18117

6.1i ECS - I/O BUFFERS do not list the LVDS I/O standard

Description

Keywords: 6.1i, ECS, LVDS, I/O, IO

Urgency: Standard

General Description:
When using the ECS schematic entry tool, the LVDS I/O standard is not listed with in any of the I/O buffer types (IBUF / IBUFG / OBUF / OBUFT).

Solution

1

LVDS buffers are included for all families. However, it might be hard to find them for Spartan-II E and Virtex-E because they are listed under Spartan-II E_IO and Virtex-E_IO categories which are at the end of the category list instead of next to all of the other I/O categories.

The LVDS buffers can be selected in a Spartan-II of Virtex schematic but will cause an NGDBUILD error because they are not valid for these devices. In Virtex-II and newer devices, the LVDS buffers are in with the main I/O category because they do not share a library with devices that do not support them. They have also been upgraded to show the two differential ports of a buffer.

Name syntax for Virtex-E and Spartan-II E:
<buf_type>_LVDS
Example: IBUF_LVDS

Name syntax for Virtex-II and later:
<buf_type>DS_LVDS
Example: IBUFDS_LVDS

2

The UCF file could be used to assign the LVDS standard to any output signal as follows:

NET "<your_net>" IOSTANDARD = LVDS;
AR# 18117
Date Created 09/24/2003
Last Updated 01/08/2006
Status Archive
Type General Article