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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" :


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