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repo2/ultimate_cart/veronica/FT816FloatSingle.v @ 446

`timescale 1ns / 1ps
// ============================================================================
// __
// \\__/ o\ (C) 2014 Robert Finch, Stratford
// \ __ / All rights reserved.
// \/_// robfinch<remove>@finitron.ca
// ||
//
// FT816FloatSingle.v
// - Single precision (40 bit) floating point accelerator
//
// This source file is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This source file is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
// SEEEEEEE SM.MMMMMM MMMMMMMM MMMMMMMM MMMMMMMM
//
// 850 LUTs 188 FF's
// 170 MHz
// ============================================================================
//
module FT816FloatSingle(rst, clk, vda, rw, ad, db, rdy);
parameter pIOAddress = 24'hFEA200;
parameter FADD = 8'd1;
parameter FSUB = 8'd2;
parameter FMUL = 8'd3;
parameter FDIV = 8'd4;
parameter FIX2FLT = 8'd5;
parameter FLT2FIX = 8'd6;
parameter MD1 = 8'd10;
parameter ABSSWP = 8'd11;
parameter ABSSWP1 = 8'd12;
parameter NORM1 = 8'd13;
parameter NORM = 8'd14;
parameter ADD = 8'd15;
parameter FCOMPL = 8'd16;
parameter FNEG = 8'd16;
parameter SWAP = 8'd17;
parameter SWPALG = 8'd18;
parameter ADDEND = 8'd19;
parameter ALGNSW = 8'd20;
parameter RTAR = 8'd21;
parameter RTLOG = 8'd22;
parameter RTLOG1 = 8'd23;
parameter FMUL1 = 8'd24;
parameter FMUL2 = 8'd25;
parameter MUL1 = 8'd26;
parameter FMUL3 = 8'd27;
parameter MUL2 = 8'd28;
parameter MDEND = 8'd29;
parameter FDIV1 = 8'd30;
parameter MD2 = 8'd31;
parameter MD3 = 8'd32;
parameter OVCHK = 8'd34;
parameter OVFL = 8'd35;
parameter DIV1 = 8'd36;
parameter IDLE = 8'd62;
parameter RESET = 8'd63;

input rst;
input clk;
input vda;
input rw;
input [23:0] ad;
inout tri [7:0] db;
output rdy;

reg [7:0] cmd;
reg [7:0] state;
reg [5:0] state_stk [31:0];
reg [4:0] sp;
reg [3:0] sign;
reg [15:0] acc;
reg [5:0] y;
reg [39:0] FAC1;
reg [39:0] FAC2;

reg [31:0] E;
wire [7:0] FAC1_exp = FAC1[39:32];
wire [31:0] FAC1_man = FAC1[31:0];
wire [7:0] FAC2_exp = FAC2[39:32];
wire [31:0] FAC2_man = FAC2[31:0];

wire [32:0] sum = FAC1_man + FAC2_man;
wire [32:0] dif = FAC2_man - E;
wire [32:0] neg = 32'h0 - FAC1_man;
// Note the carry flag must be extended manually!
wire [8:0] exp_sum = acc + FAC1_exp + {7'd0,cf}; // FMUL
wire [8:0] exp_dif = acc - FAC1_exp - {7'd0,~cf}; // FDIV
reg [39:0] rem;

reg cf,vf,nf;
reg busy;
reg [7:0] dbo;

wire eq = FAC1==FAC2;
wire gt = (FAC1[31]^FAC2[31]) ? FAC2[31] : // If the signs are different, whichever one is positive
FAC1_exp==FAC2_exp ? (FAC1_man > FAC2_man) ^ FAC1[31] : // if exponents are equal check mantissa
FAC1_exp > FAC2_exp; // else compare exponents
wire lt = !(gt|eq);
wire zf = ~|FAC1;

wire cs = vda && (ad[23:8]==pIOAddress[23:8]);
reg rdy1;
always @(posedge clk)
if (rst)
rdy1 <= 1'b1;
else
rdy1 <= cs & ~rdy1;
assign rdy = cs ? (rw ? rdy1 : 1'b1) : 1'b1;
assign db = cs & rw ? dbo : {8{1'bz}};

always @(posedge clk)
if (rst) begin
next_state(RESET);
end
else begin
cmd <= 8'h00;
if (cs & ~rw)
case(ad[7:0])
8'h00: FAC1[7:0] <= db;
8'h01: FAC1[15:8] <= db;
8'h02: FAC1[23:16] <= db;
8'h03: FAC1[31:24] <= db;
8'h04: FAC1[39:32] <= db;
8'h0F: cmd <= db;
8'h10: FAC2[7:0] <= db;
8'h11: FAC2[15:8] <= db;
8'h12: FAC2[23:16] <= db;
8'h13: FAC2[31:24] <= db;
8'h14: FAC2[39:32] <= db;
endcase

case(ad[7:0])
8'h00: dbo <= FAC1[7:0];
8'h01: dbo <= FAC1[15:8];
8'h02: dbo <= FAC1[23:16];
8'h03: dbo <= FAC1[31:24];
8'h04: dbo <= FAC1[39:32];
8'h0F: dbo <= {busy,2'b00,lt,eq,gt,zf,vf};
8'h10: dbo <= FAC2[7:0];
8'h11: dbo <= FAC2[15:8];
8'h12: dbo <= FAC2[23:16];
8'h13: dbo <= FAC2[31:24];
8'h14: dbo <= FAC2[39:32];
endcase

case(state)
RESET:
begin
sp <= 5'h00;
next_state(IDLE);
end

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

IDLE:
begin
busy <= 1'b0;
sp <= 5'h00;
case(cmd)
FADD: begin push_state(IDLE); next_state(FADD); busy <= 1'b1; end
FSUB: begin push_state(IDLE); next_state(FSUB); busy <= 1'b1; end
FMUL: begin push_state(IDLE); next_state(FMUL); busy <= 1'b1; end
FDIV: begin push_state(IDLE); next_state(FDIV); busy <= 1'b1; end
FIX2FLT: begin push_state(IDLE); next_state(FIX2FLT); busy <= 1'b1; end
FLT2FIX: begin push_state(IDLE); next_state(FLT2FIX); busy <= 1'b1; end
FNEG: begin push_state(IDLE); next_state(FCOMPL); busy <= 1'b1; end
SWAP: begin push_state(IDLE); next_state(SWAP); busy <= 1'b1; end
endcase
end

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

MD1:
begin
$display("MD1");
sign <= {sign[2:0],1'b0};
next_state(ABSSWP);
push_state(ABSSWP);
end
ABSSWP:
begin
if (~FAC1_man[31]) begin
next_state(ABSSWP1);
end
else begin
push_state(ABSSWP1);
sign <= sign + 4'd1;
next_state(FCOMPL);
end
end
ABSSWP1:
begin
cf <= 1'b1;
next_state(SWAP);
end

//-----------------------------------------------------------------------------
// Normalize
// - Decrement exponent and shift left
// - Normalization is normally the last step of an operation so it is used
// to set a couple of result flags.
//-----------------------------------------------------------------------------
NORM1:
begin
FAC1[39:32] <= FAC1[39:32] - 16'd1;
FAC1[31:0] <= {FAC1[30:0],1'b0};
next_state(NORM);
end
NORM:
begin
$display("Normalize");
if (FAC1[31]!=FAC1[30] || FAC1_exp==8'h00) begin
$display("Normal: %h",FAC1);
pop_state();
end
// If the mantissa is zero, set the the exponent to zero. Otherwise
// normalization could spin for thousands of clock cycles decrementing
// the exponent to zero.
else if (~|FAC1_man) begin
FAC1[39:32] <= 8'h0;
pop_state();
end
else
next_state(NORM1);
end

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------

ADD:
begin
FAC1[31:0] <= sum[31:0];
cf <= sum[32];
vf <= (sum[31] ^ FAC2[31]) & (1'b1 ^ FAC1[31] ^ FAC2[31]);
pop_state();
end

//-----------------------------------------------------------------------------
// Negate
//-----------------------------------------------------------------------------

// Complement FAC1
FCOMPL:
begin
$display("FCOMPL");
FAC1[31:0] <= neg[31:0];
cf <= ~neg[32];
vf <= neg[31]==FAC1[31];
next_state(ADDEND);
end

//-----------------------------------------------------------------------------
// Swap FAC1 and FAC2
//-----------------------------------------------------------------------------

SWAP:
begin
$display("Swapping FAC1 and FAC2");
FAC1 <= FAC2;
FAC2 <= FAC1;
E <= FAC2[31:0];
acc <= FAC1_exp;
pop_state();
end

//-----------------------------------------------------------------------------
// Subtract
//-----------------------------------------------------------------------------

FSUB:
begin
push_state(SWPALG);
next_state(FCOMPL);
end
SWPALG:
begin
push_state(FADD);
next_state(ALGNSW);
end

//-----------------------------------------------------------------------------
// Addition
//-----------------------------------------------------------------------------

FADD:
begin
if (FAC1_exp != FAC2_exp)
next_state(SWPALG);
else begin
push_state(ADDEND);
next_state(ADD);
end
end
ADDEND:
begin
if (!vf)
next_state(NORM);
else
next_state(RTLOG);
end
ALGNSW:
begin
if (!cf)
next_state(SWAP);
else
next_state(RTAR);
end
RTAR:
begin
cf <= FAC1_man[31];
next_state(RTLOG);
end
RTLOG:
begin
FAC1[39:32] <= FAC1[39:32] + 16'd1;
if (FAC1[39:32]==8'hFF)
next_state(OVFL);
else
next_state(RTLOG1);
end
RTLOG1:
begin
FAC1[31:0] <= {FAC1[31],FAC1[31:1]};
E[31:0] <= {FAC1[0],E[30:1]};
cf <= E[0];
pop_state();
end

//-----------------------------------------------------------------------------
// Mulyiply
//-----------------------------------------------------------------------------

FMUL:
begin
next_state(MD1);
push_state(FMUL1);
end
FMUL1:
begin
acc <= exp_sum[7:0];
cf <= exp_sum[8];
push_state(FMUL2);
next_state(MD2);
end
FMUL2:
begin
cf <= 1'b0;
next_state(MUL1);
end
MUL1:
begin
push_state(FMUL3);
next_state(RTLOG1);
end
FMUL3:
begin
if (!cf)
next_state(MUL2);
else begin
push_state(MUL2);
next_state(ADD);
end
end
MUL2:
begin
y <= y - 6'd1;
if (y!=6'd0)
next_state(MUL1);
else
next_state(MDEND);
end
MDEND:
begin
sign <= {1'b0,sign[3:1]};
if (~sign[0])
next_state(NORM);
else
next_state(FCOMPL);
end

//-----------------------------------------------------------------------------
// Divide
//-----------------------------------------------------------------------------
FDIV:
begin
push_state(FDIV1);
next_state(MD1);
end
FDIV1:
begin
acc <= exp_dif[7:0];
cf <= ~exp_dif[8];
$display("acc=%h %h %h", exp_dif, acc, FAC1_exp);
push_state(DIV1);
next_state(MD2);
end
DIV1:
begin
$display("FAC1=%h, FAC2=%h, E=%h", FAC1, FAC2, E);
y <= y - 8'd1;
FAC1[31:0] <= {FAC1[31:0],~dif[32]};
if (dif[32]) begin
FAC2[31:0] <= {FAC2[30:0],1'b0};
if (FAC2[31]) begin
next_state(OVFL);
end
else if (y!=8'd1)
next_state(DIV1);
else begin
rem <= dif;
next_state(MDEND);
end
end
else begin
FAC2[31:0] <= {dif[30:0],1'b0};
if (dif[31]) begin
next_state(OVFL);
end
else if (y!=6'd1)
next_state(DIV1);
else begin
rem <= dif;
next_state(MDEND);
end
end
end

//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
MD2:
begin
FAC1[31:0] <= 32'h0;
if (cf)
next_state(OVCHK);
else if (acc[15])
next_state(MD3);
else begin
pop_state();
next_state(NORM);
end
end
MD3:
begin
acc[7] <= ~acc[7];
FAC1[39:32] <= {~acc[7],acc[6:0]};
y <= 6'h1F;
pop_state();
end
OVCHK:
begin
if (~acc[7])
next_state(MD3);
else
next_state(OVFL);
end
OVFL:
begin
vf <= 1'b1;
next_state(IDLE);
end

//-----------------------------------------------------------------------------
// FIX2FLT
// - convert 64 bit fixed point number to floating point
//-----------------------------------------------------------------------------

FIX2FLT:
begin
FAC1[39:32] <= 8'h9E; // exponent = 30
next_state(NORM);
end

//-----------------------------------------------------------------------------
// FLT2FIX
// - convert floating point number to fixed point.
//-----------------------------------------------------------------------------

FLT2FIX:
begin
if (FAC1_exp==8'h9E)
pop_state();
else begin
push_state(FLT2FIX);
next_state(RTAR);
end
end
endcase
end

/*
DIVBY10:
begin
FAC2[39:32] <= 16'h8003;
FAC2[31] <= 1'b0; // +ve
FAC2[30:75] <= 4'hA; // 10
FAC2[74:0] <= 75'd0;
next_state(FDIV);
end
*/
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
task push_state;
input [5:0] st;
begin
state_stk[sp-5'd1] <= st;
sp <= sp - 5'd1;
end
endtask

task pop_state;
begin
next_state(state_stk[sp]);
sp <= sp + 5'd1;
end
endtask

task next_state;
input [7:0] st;
begin
state <= st;
end
endtask

endmodule
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