ID:13076 The <name> "<name>" has multiple drivers.

CAUSE: The specified node/pin has a real or potential electrical conflict involving one or more constant or tri-state drivers. A constant driver is a logic gate or I/O with no tri-state condition; consequently, it always drives its fanouts. This error occurs if, for example, the specified node/pin has one (or more) regular driver(s) and one (or more) tri-state driver(s):

	module err1(input oe, a, b, output out);

                  
		assign out = oe ? a : 1'bz;
		assign out = ~b;
 
                  
	endmodule 

               

This error also occurs if the specified node/pin has multiple constant I/O drivers:

	module err2(input a, b, inout bidir);

                  
		assign bidir = a;
		assign bidir = b;

                  
	endmodule

               

This error also occurs if the node/pin has one permanently enabled tri-state driver and one regular tri-state driver:

	module err3(input oe, a, b, output out);

                  
		assign out = oe ? a : 1'bz;
		assign out = 1'b1 ? b : 1'bz;
 
                  
	endmodule

               

Finally, this error also occurs if the node/pin has multiple tri-state drivers with conflicting enable signals. Conflicting enable signals occur in two situations:

• Two or more tri-state drivers have the same enable signal.
• Two tri-state drivers have the same enable signal but with a different polarity (positive or negative), and there is a third tri-state driver.

The following designs illustrate both types of conflicting enables:

	module err4(input a, b, oe, output out);

                  
		assign out = oe ? a : 1'bz;
		assign out = oe ? b : 1'bz;

                  
	endmodule

                  
	module err5(input a, b, c, oe1, oe2, output out);

                  
		assign out = oe1 ? a : 1'bz;
		assign out = !oe1 ? b : 1'bz;

                  
		assign out = oe2 ? c : 1'bz;

                  
	endmodule