Sequential logic circuits are modeled using edge sensitive elements in the sensitive list of always blocks. One simple way to eliminate the latch with always statement is to always drive 0 to the LHS variable in the beginning of always code as shown in the code below.ġ7 endcase 18 end 19 20 endmodule You could download file decoder_always.v here This is due to the fact that timing analysis tools always have problems with latches glitch at enable pin of latch is another problem). (No one seems to like latches in design, though they are faster, and take lesser transistor. While modeling using always statements, there is the chance of getting a latch after synthesis if care is not taken. Writing simple combinational circuits in Verilog using assign statements is very straightforward, like in the example belowĩ 10 endmodule You could download file tri_buf.v hereĨ 9 endmodule You could download file mux_21.v hereħ 8 endmodule You could download file bus_con.v hereħ 8 endmodule You could download file multiply.v hereĥ assign out = (in = 3'b000 ) ? 8'b0000_0001 : 6 (in = 3'b001 ) ? 8'b0000_0010 : 7 (in = 3'b010 ) ? 8'b0000_0100 : 8 (in = 3'b011 ) ? 8'b0000_1000 : 9 (in = 3'b100 ) ? 8'b0001_0000 : 10 (in = 3'b101 ) ? 8'b0010_0000 : 11 (in = 3'b110 ) ? 8'b0100_0000 : 12 (in = 3'b111 ) ? 8'b1000_0000 : 8'h00 ġ3 14 endmodule You could download file decoder.v hereĬombinational Circuit Modeling using always There are very few rules that need to be followed to get good synthesis output and avoid surprises.Ĭombinational Circuit Modeling using assignĬombinational circuits modeling in Verilog can be done using assign and always blocks. One is combinational circuits and the second is sequential circuits. 7 H-bridge motor control based on tri-state switches.From what we have learnt in digital design, we know that there could be only two types of digital circuits. 6 Connecting NAND - NOR gates to form AND - OR gates.įig. 3 if IC1B is connected at point X the output will be inverting. 5 Tri-State switch inverting truth table. 4 Tri-State switch non-inverting truth table.įig.
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