AR# 3590

Foundation XVHDL, CPLD: How to set global signals (tristate, set/reset, clock)


Keyword: cpld, bidirectional, tristate, set, reset, GTS, GSR.

Urgency: Standard

General Description:
In CPLD design, you can assign a signal to be global set/reset,
output enable, or clock by attaching a global attribute.
How is this done with Foundation XVHDL?
This is documented in Foundation help.


In Foundation Project Manager, click on help->Foundation help
contents. The attributes for these global signal are documented
in 2 places:
1. Under Techniques, CPLD Design Techniques->Global Nets:
Clock, 3-state, Set/Reset.

2. Under Reference, CPLD attribute->CPLD attributes used
in VHDL files.

The attributes are set as follows:
-- Declare BUFG attribute
attribute bufg: string;
-- For global clock:
attribute bufg of my_clock : signal is "CLK";
-- For global tristate output or output enable
attribute bufg of my_enable : signal is "OE";
-- For global set/reset.
attribute bufg of my_reset : signal is "SR";
AR# 3590
Date 01/02/2000
Status Archive
Type General Article