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AR# 2509

Foundation XVHDL - Cannot instantiate the XBlox TRISTATE component without pullups


Keywords: xblox, metamor, xvhdl, tristate, pullup

Urgency: Standard

General Description:
When instantiating an XBlox TRISTATE component within a Foundation XVHDL design, the synthesiser will complain if you do not pass both the ENCODING and FLOAT_VAL parameters. The only values allowed for the FLOAT_VAL parameter are PULLUP and PULLUP_D. This means that internal tristates must have pullups on the outputs. However, the documentation says that this should be an 'optional' parameter.


Open the "Xblox.vhd" file in the "C:\active\VHDL\VHDL\Vhdl_lib" directory and change the following line :

component TRISTATE is
generic (FLOAT_VAL : string;
ENCODING : string := "");


component TRISTATE is
generic (FLOAT_VAL : string :="";
ENCODING : string := "");

by inserting the extra :=""

This will allow you to omit the FLOAT_VAL parameter in your VHDL source code. The result will be internal tristates with
no pullups.
AR# 2509
Date Created 07/03/1997
Last Updated 12/06/2005
Status Archive
Type General Article