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   1 //-----------------------------------------------------------------------------
   2 // The way that we connect things in low-frequency simulation mode. In this
   3 // case just pass everything through to the ARM, which can bit-bang this
   4 // (because it is so slow).
   5 //
   6 // Jonathan Westhues, April 2006
   7 //-----------------------------------------------------------------------------
   8
   9 module lo_simulate(
  10     pck0, ck_1356meg, ck_1356megb,
  11     pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4,
  12     adc_d, adc_clk,
  13     ssp_frame, ssp_din, ssp_dout, ssp_clk,
  14     cross_hi, cross_lo,
  15     dbg,
  16          divisor
  17 );
  18     input pck0, ck_1356meg, ck_1356megb;
  19     output pwr_lo, pwr_hi, pwr_oe1, pwr_oe2, pwr_oe3, pwr_oe4;
  20     input [7:0] adc_d;
  21     output adc_clk;
  22     input ssp_dout;
  23     output ssp_frame, ssp_din, ssp_clk;
  24     input cross_hi, cross_lo;
  25     output dbg;
  26          input [7:0] divisor;
  27
  28 // No logic, straight through.
  29 assign pwr_oe3 = 1'b0;
  30 assign pwr_oe1 = ssp_dout;
  31 assign pwr_oe2 = ssp_dout;
  32 assign pwr_oe4 = ssp_dout;
  33 assign ssp_clk = cross_lo;
  34 assign pwr_lo = 1'b0;
  35 assign pwr_hi = 1'b0;
  36 assign dbg = ssp_frame;
  37
  38 // Divide the clock to be used for the ADC
  39 reg [7:0] pck_divider;
  40 reg clk_state;
  41
  42 always @(posedge pck0)
  43 begin
  44         if(pck_divider == divisor[7:0])
  45                 begin
  46                         pck_divider <= 8'd0;
  47                         clk_state = !clk_state;
  48                 end
  49         else
  50         begin
  51                 pck_divider <= pck_divider + 1;
  52         end
  53 end
  54
  55 assign adc_clk = ~clk_state;
  56
  57 // Toggle the output with hysteresis
  58 //  Set to high if the ADC value is above 200
  59 //  Set to low if the ADC value is below 64
  60 reg is_high;
  61 reg is_low;
  62 reg output_state;
  63
  64 always @(posedge pck0)
  65 begin
  66         if((pck_divider == 8'd7) && !clk_state) begin
  67                 is_high = (adc_d >= 8'd200);
  68                 is_low = (adc_d <= 8'd64);
  69         end
  70 end
  71
  72 always @(posedge is_high or posedge is_low)
  73 begin
  74         if(is_high)
  75                 output_state <= 1'd1;
  76         else if(is_low)
  77                 output_state <= 1'd0;
  78 end
  79
  80 assign ssp_frame = output_state;
  81
  82 endmodule