Verilog Operators Part-II

Verilog Operators

Part-II

源自 http://www.asic-world.com/verilog/operators2.html#Concatenation_Operator

		Reduction Operators
		Operator Description & and ~& nand | or ~| nor ^ xor ^~ or ~^ xnor
		Reduction operators are unary. They perform a bit-wise operation on a single operand to produce a single bit result. Reduction unary NAND and NOR operators operate as AND and OR respectively, but with their outputs negated. Unknown bits are treated as described before.
		Example
		1 module reduction_operators(); 2 3 initial begin 4 // Bit Wise AND reduction 5 $display (" & 4'b1001 = %b", (& 4'b1001)); 6 $display (" & 4'bx111 = %b", (& 4'bx111)); 7 $display (" & 4'bz111 = %b", (& 4'bz111)); 8 // Bit Wise NAND reduction 9 $display (" ~& 4'b1001 = %b", (~& 4'b1001)); 10 $display (" ~& 4'bx001 = %b", (~& 4'bx001)); 11 $display (" ~& 4'bz001 = %b", (~& 4'bz001)); 12 // Bit Wise OR reduction 13 $display (" | 4'b1001 = %b", (| 4'b1001)); 14 $display (" | 4'bx000 = %b", (| 4'bx000)); 15 $display (" | 4'bz000 = %b", (| 4'bz000)); 16 // Bit Wise NOR reduction 17 $display (" ~| 4'b1001 = %b", (~| 4'b1001)); 18 $display (" ~| 4'bx001 = %b", (~| 4'bx001)); 19 $display (" ~| 4'bz001 = %b", (~| 4'bz001)); 20 // Bit Wise XOR reduction 21 $display (" ^ 4'b1001 = %b", (^ 4'b1001)); 22 $display (" ^ 4'bx001 = %b", (^ 4'bx001)); 23 $display (" ^ 4'bz001 = %b", (^ 4'bz001)); 24 // Bit Wise XNOR 25 $display (" ~^ 4'b1001 = %b", (~^ 4'b1001)); 26 $display (" ~^ 4'bx001 = %b", (~^ 4'bx001)); 27 $display (" ~^ 4'bz001 = %b", (~^ 4'bz001)); 28 #10 $finish; 29 end 30 31 endmodule You could download file reduction_operators.v here
		& 4'b1001 = 0 & 4'bx111 = x & 4'bz111 = x ~& 4'b1001 = 1 ~& 4'bx001 = 1 ~& 4'bz001 = 1 | 4'b1001 = 1 | 4'bx000 = x | 4'bz000 = x ~| 4'b1001 = 0 ~| 4'bx001 = 0 ~| 4'bz001 = 0 ^ 4'b1001 = 0 ^ 4'bx001 = x ^ 4'bz001 = x ~^ 4'b1001 = 1 ~^ 4'bx001 = x ~^ 4'bz001 = x
		Shift Operators
		Operator Description << left shift >> right shift
		The left operand is shifted by the number of bit positions given by the right operand. The vacated bit positions are filled with zeroes.
		Example
		1 module shift_operators(); 2 3 initial begin 4 // Left Shift 5 $display (" 4'b1001 << 1 = %b", (4'b1001 << 1)); 6 $display (" 4'b10x1 << 1 = %b", (4'b10x1 << 1)); 7 $display (" 4'b10z1 << 1 = %b", (4'b10z1 << 1)); 8 // Right Shift 9 $display (" 4'b1001 >> 1 = %b", (4'b1001 >> 1)); 10 $display (" 4'b10x1 >> 1 = %b", (4'b10x1 >> 1)); 11 $display (" 4'b10z1 >> 1 = %b", (4'b10z1 >> 1)); 12 #10 $finish; 13 end 14 15 endmodule You could download file shift_operators.v here
		4'b1001 << 1 = 0010 4'b10x1 << 1 = 0x10 4'b10z1 << 1 = 0z10 4'b1001 >> 1 = 0100 4'b10x1 >> 1 = 010x 4'b10z1 >> 1 = 010z
		Concatenation Operator
		Concatenations are expressed using the brace characters { and }, with commas separating the expressions within. Example: + {a, b[3:0], c, 4'b1001} // if a and c are 8-bit numbers, the results has 24 bits Unsized constant numbers are not allowed in concatenations.
		Example
		1 module concatenation_operator(); 2 3 initial begin 4 // concatenation 5 $display (" {4'b1001,4'b10x1} = %b", {4'b1001,4'b10x1}); 6 #10 $finish; 7 end 8 9 endmodule You could download file concatenation_operator.v here
		{4'b1001,4'b10x1} = 100110x1
		Replication Operator
		Replication operator is used to replicate a group of bits n times. Say you have a 4 bit variable and you want to replicate it 4 times to get a 16 bit variable: then we can use the replication operator.
		Operator Description {n{m}} Replicate value m, n times
		Repetition multipliers (must be constants) can be used: {3{a}} // this is equivalent to {a, a, a} Nested concatenations and replication operator are possible: {b, {3{c, d}}} // this is equivalent to {b, c, d, c, d, c, d}
		Example
		1 module replication_operator(); 2 3 initial begin 4 // replication 5 $display (" {4{4'b1001}} = %b", {4{4'b1001}}); 6 // replication and concatenation 7 $display (" {4{4'b1001,1'bz}} = %b", {4{4'b1001,1'bz}}); 8 #10 $finish; 9 end 10 11 endmodule You could download file replication_operator.v here
		{4{4'b1001} = 1001100110011001 {4{4'b1001,1'bz} = 1001z1001z1001z1001z
		Conditional Operators
		The conditional operator has the following C-like format: cond_expr ? true_expr : false_expr The true_expr or the false_expr is evaluated and used as a result depending on what cond_expr evaluates to (true or false).
		Example
		1 module conditional_operator(); 2 3 wire out; 4 reg enable,data; 5 // Tri state buffer 6 assign out = (enable) ? data : 1'bz; 7 8 initial begin 9 $display ("time\t enable data out"); 10 $monitor ("%g\t %b %b %b",$time,enable,data,out); 11 enable = 0; 12 data = 0; 13 #1 data = 1; 14 #1 data = 0; 15 #1 enable = 1; 16 #1 data = 1; 17 #1 data = 0; 18 #1 enable = 0; 19 #10 $finish; 20 end 21 22 endmodule You could download file conditional_operator.v here
		time enable data out 0 0 0 z 1 0 1 z 2 0 0 z 3 1 0 0 4 1 1 1 5 1 0 0 6 0 0 z
		Operator Precedence
		Operator Symbols Unary, Multiply, Divide, Modulus !, ~, *, /, % Add, Subtract, Shift +, - , <<, >> Relation, Equality <,>,<=,>=,==,!=,===,!== Reduction &, !&,^,^~,|,~| Logic &&, || Conditional ? :