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 `ifdef verilator
  12 `else
  13         , output reg [8:0] sys_odata = 0,
  14         input [8:0] sys_idata,
  15         output reg sys_tookdata = 0
  16 `endif
  17 );
  18
  19         /* Terminal pretends to be cp5. */
  20         reg towrite = 0;
  21         reg [7:0] data = 0;
  22         reg [8:0] indata = 0;   /* High bit is if data is present. */
  23         reg didread = 0;
  24
  25         always @(*)
  26         begin
  27                 towrite = 0;
  28                 data = 8'hxx;
  29                 cp_ack = 0;
  30                 cp_busy = 0;
  31                 cp_read = 0;
  32                 didread = 0;
  33                 if (cp_req && (cp_rnw == 0) && (cp_insn[27:24] == 4'b1110) && (cp_insn[19:16] == 4'b0000) && (cp_insn[11:8] == 4'h5))
  34                 begin
  35                         towrite = 1;
  36                         data = cp_write[7:0];
  37                         cp_ack = 1;
  38                 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))
  39                 begin
  40                         cp_read = {23'h0, indata[8:0]};
  41                         cp_ack = 1;
  42                         didread = cp_insn[7:5] == 1;
  43                 end
  44         end
  45 `ifdef verilator
  46         always @(posedge clk)
  47                 if (towrite)
  48                         $c("{extern void term_output(unsigned char d); term_output(",data,");}");
  49                 else if (didread || !indata[8])
  50                         indata = $c("({extern unsigned int term_input(); term_input();})");
  51 `else
  52         always @(posedge clk)
  53         begin
  54                 sys_odata = {towrite,data};
  55                 if (didread || !indata[8])
  56                 begin
  57                         indata = sys_idata;
  58                         sys_tookdata = 1;
  59                 end else
  60                         sys_tookdata = 0;
  61         end
  62 `endif
  63 endmodule