package Top;

import Counter::*;
import StmtFSM::*;

typedef struct {
   Integer     active;
   Integer     fporch;
   Integer     sync;
   Integer     bporch;
} SyncDescriptor;

SyncDescriptor horizontal = SyncDescriptor{
   active: 640,
   fporch: 16,
   sync: 96,
   bporch: 48
};

SyncDescriptor vertical = SyncDescriptor{
   active: 480,
   fporch: 10,
   sync: 2,
   bporch: 33
};

interface SyncGenerator;
   method    Action      tick();
   method    Bool        preedge();
   method    Bool        out_n();
   method    Bool        out();
   method    Bool        active();
endinterface

interface ITop;
   (* always_ready *)
   method Bool paint();
   (* always_ready *)
   method Bool hsync();
   (* always_ready *)
   method Bool vsync();
endinterface

(* synthesize *)
module mkTop (ITop);
   Reg#(Bool) rPaint <- mkReg(False);
   Reg#(Bool) rHsync <- mkReg(False);
   Reg#(Bool) rVsync <- mkReg(False);

   let blank_line_fsm = seq
                           // Sync pulse
                           repeat (96) rHsync <= True;

                           // Back porch
                           repeat (48) rHsync <= False;

                           // Visible area
                           repeat (640) noAction;

                           // Front porch
                           repeat (16) noAction;
                        endseq;
   let video_line_fsm = seq
                           // Sync pulse
                           repeat (96) rHsync <= True;

                           // Back porch
                           repeat (48) rHsync <= False;

                           // Visible area
                           repeat (640) rPaint <= True;

                           // Front porch
                           repeat (16) rPaint <= False;
                        endseq;
   let frame_fsm = seq
                      while (True) seq
                         // Sync pulse
                         repeat (2) par
                                       rVsync <= True;
                                       blank_line_fsm;
                                    endpar

                         // Back porch
                         repeat (33) par
                                        rVsync <= False;
                                        blank_line_fsm;
                                     endpar

                         // Visible area
                         repeat (480) video_line_fsm;

                         // Front porch
                         repeat (10) blank_line_fsm;
                      endseq
                   endseq;
   let fsm <- mkFSM(frame_fsm);

   rule run_timing (fsm.done());
      fsm.start();
   endrule

   method Bool paint = rPaint._read;
   method Bool hsync = rHsync._read;
   method Bool vsync = rVsync._read;
endmodule

endpackage