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// module name
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//`define CNT_MODULE_NAME sd_counter
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// counter type = [BINARY, GRAY, LFSR]
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//`define CNT_TYPE_BINARY
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`define CNT_TYPE_GRAY
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//`define CNT_TYPE_LFSR
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// q as output
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`define CNT_Q
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// for gray type counter optional binary output
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`define CNT_Q_BIN
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// number of CNT bins
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`define CNT_LENGTH 9
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// clear
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//`define CNT_CLEAR
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// set
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//`define CNT_SET
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`define CNT_SET_VALUE `CNT_LENGTH'h9
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// wrap around creates shorter cycle than maximum length
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//`define CNT_WRAP
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`define CNT_WRAP_VALUE `CNT_LENGTH'h9
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// clock enable
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`define CNT_CE
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// q_next as an output
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//`define CNT_QNEXT
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// q=0 as an output
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//`define CNT_Z
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// q_next=0 as a registered output
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//`define CNT_ZQ
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`define LFSR_LENGTH `CNT_LENGTH
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module sd_counter
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(
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`ifdef CNT_TYPE_GRAY
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output reg [`CNT_LENGTH:1] q,
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`ifdef CNT_Q_BIN
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output [`CNT_LENGTH:1] q_bin,
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`endif
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`else
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`ifdef CNT_Q
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output [`CNT_LENGTH:1] q,
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`endif
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`endif
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`ifdef CNT_CLEAR
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input clear,
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`endif
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`ifdef CNT_SET
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input set,
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`endif
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`ifdef CNT_REW
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input rew,
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`endif
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`ifdef CNT_CE
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input cke,
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`endif
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`ifdef CNT_QNEXT
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output [`CNT_LENGTH:1] q_next,
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`endif
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`ifdef CNT_Z
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output z,
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`endif
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`ifdef CNT_ZQ
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output reg zq,
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`endif
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input clk,
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input rst
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);
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`ifdef CNT_SET
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parameter set_value = `CNT_SET_VALUE;
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`endif
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`ifdef CNT_WRAP
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parameter wrap_value = `CNT_WRAP_VALUE;
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`endif
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// internal q reg
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reg [`CNT_LENGTH:1] qi;
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`ifdef CNT_QNEXT
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`else
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wire [`CNT_LENGTH:1] q_next;
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`endif
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`ifdef CNT_REW
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wire [`CNT_LENGTH:1] q_next_fw;
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wire [`CNT_LENGTH:1] q_next_rew;
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`endif
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`ifdef CNT_REW
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`else
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assign q_next =
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`endif
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`ifdef CNT_REW
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assign q_next_fw =
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`endif
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`ifdef CNT_CLEAR
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clear ? `CNT_LENGTH'd0 :
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`endif
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`ifdef CNT_SET
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set ? set_value :
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`endif
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`ifdef CNT_WRAP
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(qi == wrap_value) ? `CNT_LENGTH'd0 :
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`endif
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`ifdef CNT_TYPE_LFSR
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{qi[8:1],~(q[`LFSR_LENGTH]^q[1])};
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`else
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qi + `CNT_LENGTH'd1;
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`endif
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`ifdef CNT_REW
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assign q_next_rew =
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`ifdef CNT_CLEAR
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clear ? `CNT_LENGTH'd0 :
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`endif
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`ifdef CNT_SET
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set ? set_value :
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`endif
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`ifdef CNT_WRAP
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(qi == `CNT_LENGTH'd0) ? wrap_value :
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`endif
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`ifdef CNT_TYPE_LFSR
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{~(q[1]^q[2]),qi[`CNT_LENGTH:2]};
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`else
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qi - `CNT_LENGTH'd1;
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`endif
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`endif
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`ifdef CNT_REW
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assign q_next = rew ? q_next_rew : q_next_fw;
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`endif
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always @ (posedge clk or posedge rst)
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if (rst)
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qi <= `CNT_LENGTH'd0;
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else
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`ifdef CNT_CE
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if (cke)
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`endif
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qi <= q_next;
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`ifdef CNT_Q
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`ifdef CNT_TYPE_GRAY
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always @ (posedge clk or posedge rst)
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if (rst)
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q <= `CNT_LENGTH'd0;
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else
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`ifdef CNT_CE
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if (cke)
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`endif
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q <= (q_next>>1) ^ q_next;
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`ifdef CNT_Q_BIN
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assign q_bin = qi;
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`endif
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`else
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assign q = q_next;
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`endif
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`endif
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`ifdef CNT_Z
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assign z = (q == `CNT_LENGTH'd0);
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`endif
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`ifdef CNT_ZQ
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always @ (posedge clk or posedge rst)
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if (rst)
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zq <= 1'b1;
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else
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`ifdef CNT_CE
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if (cke)
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`endif
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zq <= q_next == `CNT_LENGTH'd0;
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`endif
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endmodule
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