Answers Database

Foundation XVHDL: Cannot instantiate the XBlox TRISTATE component without pullups.


Record #2509

Product Family:  Software

Product Line:  Metamor

Problem Title:
Foundation XVHDL:  Cannot instantiate the XBlox TRISTATE component
without pullups.



Problem Description:
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.


Solution 1:

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 := "");

to

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.



End of Record #2509