////////////////////////////////////////////////////////////////////////
//
// Project Reality
//
// module:	bl
// description:	Top level for blend unit.
//
// designer:	Phil Gossett
// date:	6/22/95
//
////////////////////////////////////////////////////////////////////////

module bl (clk, start_gclk, st_span, ncyc,
	z_source_select, antialias_enable,
	z_compare_enable, z_update_enable, z_mode,
	cvg_dest, color_on_cvg, force_blend, mask15b,
	bl_p_sel_0_r, bl_m_sel_0_r, bl_a_sel_0_r, bl_b_sel_0_r,
	bl_p_sel_1_r, bl_m_sel_1_r, bl_a_sel_1_r, bl_b_sel_1_r,
	blend_r, blend_g, blend_b, fog_r, fog_g, fog_b, fog_a,
	pixel_r, pixel_g, pixel_b, pixel_a, pixel_cvg,
	shade_a, st_z, dzdx, dzdy, prim_z, prim_delta_z,
	mem_r, mem_g, mem_b, mem_a, mem_z,
	span_r, span_g, span_b, span_a, span_z,
	span_color_we, span_depth_we);

input clk;
input start_gclk;
input st_span;
input ncyc;
input z_source_select;
input antialias_enable;
input z_compare_enable;
input z_update_enable;
input [1:0] z_mode;
input [1:0] cvg_dest;
input color_on_cvg;
input force_blend;
input mask15b;
input [1:0] bl_p_sel_0_r;
input [1:0] bl_m_sel_0_r;
input [1:0] bl_a_sel_0_r;
input [1:0] bl_b_sel_0_r;
input [1:0] bl_p_sel_1_r;
input [1:0] bl_m_sel_1_r;
input [1:0] bl_a_sel_1_r;
input [1:0] bl_b_sel_1_r;
input [7:0] blend_r;
input [7:0] blend_g;
input [7:0] blend_b;
input [7:0] fog_r;
input [7:0] fog_g;
input [7:0] fog_b;
input [7:0] fog_a;
input [7:0] pixel_r;
input [7:0] pixel_g;
input [7:0] pixel_b;
input [8:0] pixel_a;	// 1.8
input [3:0] pixel_cvg;	// 1.3
input [7:0] shade_a;	// piped thru CC
input [17:0] st_z;	// stepped integer z (0,15.3)
input [15:0] dzdx;	// S.15 attributes
input [15:0] dzdy;
input [15:0] prim_z;	// 16.0
input [15:0] prim_delta_z;
input [7:0] mem_r;	// from mem_span unit
input [7:0] mem_g;
input [7:0] mem_b;
input [2:0] mem_a;
input [17:0] mem_z;	// z and delta from memory (fp format)

output [7:0] span_r;	// to mem_span unit
output [7:0] span_g;
output [7:0] span_b;
output [2:0] span_a;
output [17:0] span_z;	// z and delta to memory (fp format)
output span_color_we;
output span_depth_we;

reg force_cycle;
reg pre_cycle;

wire [1:0] min_exp_delta_z;
wire [3:0] max_old_delta_z;
wire [4:0] inc_old_delta_z;
wire [3:0] adj_old_delta_z;
wire [15:0] pp_new_delta_z; // 16.0
wire [15:0] pp_old_delta_z; // 16.0
wire [17:0] pp_old_z;	// 0,15.3
wire [3:0] norm_delta_z; // log2
wire [2:0] p_norm_a;
wire [2:0] p_norm_b;

reg blend_cycle;
reg reg_z_source_select;
reg delta_z_overflow;
reg [15:0] p_new_delta_z; // 16.0
reg [15:0] p_old_delta_z; // 16.0
reg [17:0] p_old_z;	// 0,15.3
reg [1:0] bl_p_sel_reg;
reg [1:0] bl_a_sel_reg;
reg [1:0] bl_m_sel_reg;
reg [1:0] bl_b_sel_reg;
reg [2:0] norm_a;
reg [2:0] norm_b;
reg [8:0] pixel_a_reg;	// 1.8
reg [3:0] pixel_c_reg;	// 1.3

wire [8:0] pixel_alpha;	// 1.8
wire [15:0] pp_delta_z;	// 16.0
wire [3:0] p_delta_z;	// log2
wire [17:0] p_new_z;	// 0,15.3
wire p_farther;
wire p_nearer;
wire p_infront;
wire [7:0] x_r;
wire [7:0] x_g;
wire [7:0] x_b;
wire [7:0] p_r;
wire [7:0] p_g;
wire [7:0] p_b;
wire [7:0] m_r;
wire [7:0] m_g;
wire [7:0] m_b;
wire [5:0] a;		// 1.5
wire [4:0] b;		// 0.5
wire [5:0] a_norm;
wire [4:0] b_norm;
wire lsen;
wire [10:0] mp_r;	// 0.11
wire [10:0] mp_g;
wire [10:0] mp_b;
wire [3:0] mp_c;	// 1.3

reg [15:0] new_delta_z;	// 16.0
reg [17:0] new_z;	// 0,15.3
reg [17:0] old_z;	// 0,15.3
reg [3:0] delta_z;	// log2
reg max_z;
reg farther;
reg nearer;
reg infront;
reg [3:0] pixel_cvg_reg;
reg [2:0] mem_a_reg;
reg [7:0] p_r_reg;
reg [7:0] p_g_reg;
reg [7:0] p_b_reg;
reg [7:0] m_r_reg;
reg [7:0] m_g_reg;
reg [7:0] m_b_reg;
reg [10:0] bl_r;	// 0.11
reg [10:0] bl_g;
reg [10:0] bl_b;
reg [3:0] bl_c;		// 1.3
reg p_alpha_one;

wire [13:0] p_span_z;	// fp: 11 mant, 3 exp
wire [3:0] p_span_delta_z; //log2
wire [7:0] dv_r;
wire [7:0] dv_g;
wire [7:0] dv_b;
wire [3:0] pixel_cvg_pre2;
wire pre_cvg_wrap;
wire we_cvg;

reg force_blend_reg;
reg blend_en;
reg trans;
reg decal;
reg opaque;
reg pp_span_color_we;
reg pre_span_color_we;
reg [3:0] pixel_cvg_rg2;
reg [2:0] mem_a_rg2;
reg cvg_wrap;
reg [7:0] p_r_rg2;
reg [7:0] p_g_rg2;
reg [7:0] p_b_rg2;
reg [7:0] m_r_rg2;
reg [7:0] m_g_rg2;
reg [7:0] m_b_rg2;
reg [7:0] bl_r_rg2;
reg [7:0] bl_g_rg2;
reg [7:0] bl_b_rg2;
reg [7:0] dv_r_rg2;
reg [7:0] dv_g_rg2;
reg [7:0] dv_b_rg2;
reg span_depth_we;
reg [17:0] span_z;
reg alpha_one;

wire [2:0] pre_span_a;

reg span_color_we;
reg [7:0] span_r;
reg [7:0] span_g;
reg [7:0] span_b;
reg [2:0] span_a;

// pipeline stage -1
always @(posedge clk)
  if (start_gclk) begin
	force_cycle = st_span || pre_cycle;
	pre_cycle <= !(force_cycle || !ncyc);
  end

assign min_exp_delta_z = {2{!mem_z[17]}} & ~mem_z[16:15];
assign max_old_delta_z = (mem_z[3] ||
			  mem_z[2] ||
			 (mem_z[1] && !min_exp_delta_z[1]) ||
			((mem_z[1] ^~  min_exp_delta_z[1]) &&
                         (mem_z[0] && !min_exp_delta_z[0]))) ?
			mem_z[3:0] : {2'b0,min_exp_delta_z};
assign inc_old_delta_z = (!mem_z[17] && !(mem_z[16] && mem_z[15])) ?
			(max_old_delta_z + 1) : max_old_delta_z;
assign adj_old_delta_z = {4{inc_old_delta_z[4]}} | inc_old_delta_z[3:0];

// don't optimize the following instanced stuff:
bl_deltaz bldz (.sel(z_source_select), .prim(prim_delta_z),
		            .dzdx(dzdx), .dzdy(dzdy),
		            .deltaz(pp_new_delta_z));
bl_exp    fexp (.i(adj_old_delta_z), .z(pp_old_delta_z));
bl_dec    fdec (.i(mem_z[17:4]), .z(pp_old_z));
bl_log    flgn (.i(pp_new_delta_z), .z(norm_delta_z));
bl_norm   blnm (.new(norm_delta_z), .old(mem_z[3:0]),
		.norma(p_norm_a), .normb(p_norm_b));

// pipeline stage 0
always @(posedge clk)
  if (start_gclk) begin
	blend_cycle  <= pre_cycle;
	reg_z_source_select <= z_source_select;
	delta_z_overflow <= inc_old_delta_z[4];
	p_new_delta_z <= pp_new_delta_z;
	p_old_delta_z <= pp_old_delta_z;
	p_old_z <= pp_old_z;
	norm_a	<= p_norm_a;
	norm_b	<= p_norm_b;
	bl_p_sel_reg <= pre_cycle ? bl_p_sel_1_r : bl_p_sel_0_r;
	bl_m_sel_reg <= pre_cycle ? bl_m_sel_1_r : bl_m_sel_0_r;
	bl_a_sel_reg <= pre_cycle ? bl_a_sel_1_r : bl_a_sel_0_r;
	bl_b_sel_reg <= pre_cycle ? bl_b_sel_1_r : bl_b_sel_0_r;
	pixel_a_reg <= pixel_a;
	pixel_c_reg <= pixel_cvg;
  end

assign	pixel_alpha = blend_cycle ? pixel_a_reg : pixel_a;

assign	p_new_z = reg_z_source_select ? {prim_z[14:0],3'b000} : st_z;

// don't optimize the following instanced stuff:
bl_max maxz (	.a(p_new_delta_z), .b(p_old_delta_z), .z(pp_delta_z));
bl_log flgd (	.i(pp_delta_z), .z(p_delta_z));
bl_zcomp zcmp (	.old(p_old_z), .new(p_new_z), .delta(pp_delta_z),
		.farther(p_farther), .nearer(p_nearer), .infront(p_infront));

bl_mux8 mxxr (.s(blend_cycle), .i0i(pixel_r), .i1i(bl_r[10:3]), .z(x_r));
bl_mux8 mxxg (.s(blend_cycle), .i0i(pixel_g), .i1i(bl_g[10:3]), .z(x_g));
bl_mux8 mxxb (.s(blend_cycle), .i0i(pixel_b), .i1i(bl_b[10:3]), .z(x_b));

bl_mxpm mxpr (.s(bl_p_sel_reg),	.i0i(x_r),
				.i1i(mem_r),
				.i2i(blend_r),
				.i3i(fog_r),		.z(p_r));
bl_mxpm mxpg (.s(bl_p_sel_reg),	.i0i(x_g),
				.i1i(mem_g),
				.i2i(blend_g),
				.i3i(fog_g),		.z(p_g));
bl_mxpm mxpb (.s(bl_p_sel_reg),	.i0i(x_b),
				.i1i(mem_b),
				.i2i(blend_b),
				.i3i(fog_b),		.z(p_b));

bl_mxpm mxmr (.s(bl_m_sel_reg),	.i0i(x_r),
				.i1i(mem_r),
				.i2i(blend_r),
				.i3i(fog_r),		.z(m_r));
bl_mxpm mxmg (.s(bl_m_sel_reg),	.i0i(x_g),
				.i1i(mem_g),
				.i2i(blend_g),
				.i3i(fog_g),		.z(m_g));
bl_mxpm mxmb (.s(bl_m_sel_reg),	.i0i(x_b),
				.i1i(mem_b),
				.i2i(blend_b),
				.i3i(fog_b),		.z(m_b));

bl_muxa muxa (.s(bl_a_sel_reg),	.i0i(pixel_alpha[8:3]),
				.i1i({1'b0,fog_a[7:3]}),
				.i2i({1'b0,shade_a[7:3]}),
				.i3i(6'b000000),	.z(a));
bl_muxb muxb (.s(bl_b_sel_reg),	.i0n(a[4:0]),	// note this input negated
				.i1i({mem_a,2'b0}),
				.i2i(5'b11111),
				.i3i(5'b00000),		.z(b));

// if mem cvg, ls 2 bits of alphas not enabled, else norms ignored
assign lsen = (bl_b_sel_reg == 2'b01);
bl_nrma nrma (.lsen(lsen), .sh(norm_a), .i(a),		.z(a_norm));
bl_nrmb nrmb (.lsen(lsen), .sh(norm_b), .i(b),		.z(b_norm));

bl_lerp bllerpr (.p(p_r), .m(m_r), .a(a_norm), .b(b_norm), .mp(mp_r));
bl_lerp bllerpg (.p(p_g), .m(m_g), .a(a_norm), .b(b_norm), .mp(mp_g));
bl_lerp bllerpb (.p(p_b), .m(m_b), .a(a_norm), .b(b_norm), .mp(mp_b));

bl_add  bladd   (.a(a_norm[5:2]), .b(b_norm[4:2]),          .s(mp_c));

// pipeline stage 1
always @(posedge clk)
  if (start_gclk) begin
	new_delta_z <= p_new_delta_z;
	delta_z <= p_delta_z;
	old_z <= p_old_z;
	new_z <= p_new_z;
	max_z   <= &p_old_z;
	farther <= p_farther || delta_z_overflow;
	nearer  <= p_nearer  || delta_z_overflow;
	infront <= p_infront;

	pixel_cvg_reg <= blend_cycle ? pixel_c_reg : pixel_cvg;
	mem_a_reg <= mem_a;

	p_r_reg <= p_r;
	p_g_reg <= p_g;
	p_b_reg <= p_b;

	m_r_reg <= m_r;
	m_g_reg <= m_g;
	m_b_reg <= m_b;

	bl_r    <= mp_r;
	bl_g    <= mp_g;
	bl_b    <= mp_b;

	bl_c    <= mp_c;

	p_alpha_one <= (bl_a_sel_reg == 2'b0) && (bl_b_sel_reg == 2'b0) &&
		(pixel_alpha[8] || (pixel_alpha[7:0] == 8'b11111111));
  end

// don't optimize the following instanced stuff:
bl_log  flgs (.i(new_delta_z), .z(p_span_delta_z));
bl_enc  fenc (.i(new_z), .z(p_span_z));

bl_cvg2 blcvg2  (.pcvg(pixel_cvg_reg), .mcvg(mem_a_reg),
		 .newz(new_z), .oldz(old_z), .deltaz(delta_z),
		 .zmode(z_mode), .infront(infront), .farther(farther),
		 .pout(pixel_cvg_pre2), .wrap(pre_cvg_wrap), .we(we_cvg));

bl_div bldivr (.n(bl_r), .d(bl_c), .q(dv_r));
bl_div bldivg (.n(bl_g), .d(bl_c), .q(dv_g));
bl_div bldivb (.n(bl_b), .d(bl_c), .q(dv_b));

// pipeline stage 2
always @(posedge clk)
  if (start_gclk) begin
	force_blend_reg <= force_blend;
	blend_en <= force_blend ||
			(farther && !pre_cvg_wrap && antialias_enable);
	trans  = !z_mode[0] && z_mode[1] && (max_z | infront);
	decal  =  z_mode[0] && z_mode[1] && !max_z && nearer && farther;
	opaque =              !z_mode[1] && (max_z |
					(pre_cvg_wrap ? infront : nearer));
	pp_span_color_we = (antialias_enable ? we_cvg : mask15b) &&
			(!z_compare_enable || trans || decal || opaque);
	pre_span_color_we <= pp_span_color_we;

	pixel_cvg_rg2 <= pixel_cvg_pre2;
	mem_a_rg2 <= mem_a_reg;
	cvg_wrap <= pre_cvg_wrap;

	p_r_rg2  <= p_r_reg;
	p_g_rg2  <= p_g_reg;
	p_b_rg2  <= p_b_reg;

	m_r_rg2  <= m_r_reg;
	m_g_rg2  <= m_g_reg;
	m_b_rg2  <= m_b_reg;

	bl_r_rg2 <= bl_r[10:3];
	bl_g_rg2 <= bl_g[10:3];
	bl_b_rg2 <= bl_b[10:3];

	dv_r_rg2 <= dv_r;
	dv_g_rg2 <= dv_g;
	dv_b_rg2 <= dv_b;

	span_z <= {p_span_z,p_span_delta_z};
	span_depth_we <= pp_span_color_we && z_update_enable;

	alpha_one <= p_alpha_one;
  end

// don't optimize the following instanced stuff:
bl_cvg3 blcvg3  (.pcvg(pixel_cvg_rg2), .mcvg(mem_a_rg2),
		 .dest(cvg_dest), .en(blend_en),
		 .alpha(pre_span_a));

// pipeline stage 3
always @(posedge clk)
  if (start_gclk) begin
	span_r <= (color_on_cvg && !cvg_wrap) ?
			m_r_rg2 :
			((blend_en && !alpha_one) ?
				(force_blend_reg ? bl_r_rg2 : dv_r_rg2) :
				p_r_rg2);
	span_g <= (color_on_cvg && !cvg_wrap) ?
			m_g_rg2 :
			((blend_en && !alpha_one) ?
				(force_blend_reg ? bl_g_rg2 : dv_g_rg2) :
				p_g_rg2);
	span_b <= (color_on_cvg && !cvg_wrap) ?
			m_b_rg2 :
			((blend_en && !alpha_one) ?
				(force_blend_reg ? bl_b_rg2 : dv_b_rg2) :
				p_b_rg2);
	span_a <= pre_span_a;
	span_color_we <= pre_span_color_we;
  end

endmodule // bl