Answers Database


FPGA Compiler, Design Compiler: How do I pass the IOSTANDARD constraint for Virtex designs?


Record #8254

Product Family: Software

Product Line: Synopsys

Product Part: FPGA Compiler

Product Version: 1999.05

Problem Title:

FPGA Compiler, Design Compiler:	How do I pass the IOSTANDARD constraint for Virtex designs?


Problem Description:
Urgency: Standard

General Description:
In the $XILINX/synopsys/examples the template.synopsys_dc.setup_virtex does not have the option to pass through the IOSTANDARD constraint.

How do I specify special Virtex I/O standards on my ports?


Solution 1:

The I/O standards may be instantiated in your HDL code along with the I/O buffers. The names of
these components follow the <buffer_type>_<standard> convention, like this: IBUF_GTL

When these buffers are instantiated, they must not be included during the set_port_is_pad command. Therefore, when calling set_port_is_pad, either list only the ports that do not have buffers inserted:

set_port_is_pad {CLK, RST, DOUT}

or, set this attribute on all ports, then remove it for those ports that have instantiated I/O buffers:

set_port_is_pad "*"
remove_attribute {DIN} port_is_pad



Solution 2:

One option is to specify these standards in the synthesis compilation script. After running "set_port_is_pad", use this syntax to specify an I/O standard:

set_pad_type -exact <buffer_type>_<standard> {<port_list>}

where <buffer_type> represents the type of buffer to be inserted, <standard> represents an I/O
standard and <port_list> represents the ports to receive this standard. For example:

set_pad_type -exact IBUF_GTL {DIN}



Solution 3:

The IOSTANDARD attribute can always be applied via the UCF file. This does not affect the Synopsys flow whatsoever. Here is the UCF syntax:

NET <port_name> IOSTANDARD = <standard>;

For example:

NET DIN IOSTANDARD = GTS ;




End of Record #8254 - Last Modified: 12/20/99 15:38

For the latest news, design tips, and patch information on the Xilinx design environment, check out the Technical Tips!