Terminal.v

   1 module Terminal(
   2         input clk,
   3
   4         input cp_req,
   5         input [31:0] cp_insn,
   6         output reg cp_ack,
   7         output reg cp_busy,
   8         input cp_rnw,
   9         output reg [31:0] cp_read = 0,
  10         input [31:0] cp_write);
  11
  12         /* Terminal pretends to be cp5. */
  13         reg towrite = 0;
  14         reg [7:0] data = 0;
  15         reg [8:0] indata = 0;   /* High bit is if data is present. */
  16         reg didread = 0;
  17
  18         always @(*)
  19         begin
  20                 towrite = 0;
  21                 data = 8'hxx;
  22                 cp_ack = 0;
  23                 cp_busy = 0;
  24                 cp_read = 0;
  25                 didread = 0;
  26                 if (cp_req && (cp_rnw == 0) && (cp_insn[27:24] == 4'b1110) && (cp_insn[19:16] == 4'b0000) && (cp_insn[11:8] == 4'h5))
  27                 begin
  28                         towrite = 1;
  29                         data = cp_write[7:0];
  30                         cp_ack = 1;
  31                 end else if (cp_req && (cp_rnw == 1) && (cp_insn[27:24] == 4'b1110) && (cp_insn[19:16] == 4'b0001) && (cp_insn[11:8] == 4'h5))
  32                 begin
  33                         cp_read = {23'h0, indata[8:0]};
  34                         cp_ack = 1;
  35                         didread = cp_insn[7:5] == 1;
  36                 end
  37         end
  38 `ifdef verilator
  39         always @(posedge clk)
  40                 if (towrite)
  41                         $c("{extern void term_output(unsigned char d); term_output(",data,");}");
  42                 else if (didread || !indata[8])
  43                         indata = $c("({extern unsigned int term_input(); term_input();})");
  44 `endif
  45 endmodule