Bus contention checking

Bus contention checking detects bus fights on nodes that have multiple drivers. A bus fight occurs when two or more drivers drive a node with the same strength and that strength is the strongest of all drivers currently driving the node. The following table provides some examples for two drivers driving a std_logic signal:

driver 1	driver 2	fight
Z	Z	no
0	0	yes
1	Z	no
0	1	yes
L	1	no
L	H	yes

Detection of a bus fight results in an error message specifying the node and its drivers' current driving values. If a node's drivers later change value and the node is still in contention, a message is issued giving the new values of the drivers. A message is also issued when the contention ends. The bus contention checking commands can be used on VHDL and Verilog designs.

These bus checking commands are in "Commands" :

• check contention add
• check contention config
• check contention off

Model Technology Incorporated Voice: (503) 641-1340 Fax: (503)526-5410 www.model.com sales@model.com