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YosysJS Example Application #02
// borrowed with some modifications from // http://www.ee.ed.ac.uk/~gerard/Teach/Verilog/manual/Example/lrgeEx2/cooley.html module up3down5(clock, data_in, up, down, carry_out, borrow_out, count_out, parity_out); input [8:0] data_in; input clock, up, down; output reg [8:0] count_out; output reg carry_out, borrow_out, parity_out; reg [9:0] cnt_up, cnt_dn; reg [8:0] count_nxt; always @(posedge clock) begin cnt_dn = count_out - 3'b 101; cnt_up = count_out + 2'b 11; case ({up,down}) 2'b 00 : count_nxt = data_in; 2'b 01 : count_nxt = cnt_dn; 2'b 10 : count_nxt = cnt_up; 2'b 11 : count_nxt = count_out; default : count_nxt = 9'bX; endcase parity_out <= ^count_nxt; carry_out <= up & cnt_up[9]; borrow_out <= down & cnt_dn[9]; count_out <= count_nxt; end endmodule