Dual boot ROM support, and the first proof that cellular ram works!

[fpgaboy.git] / GBZ80Core.v

diff --git a/GBZ80Core.v b/GBZ80Core.v
index af5574fd2892cd056bcb3a2c1d1da16d9f654fe5..e1aa3087b0a94f4cb7e422c3160b7849bf334c5a 100644 (file)
--- a/GBZ80Core.v
+++ b/GBZ80Core.v
@@ -40,35 +40,45 @@
 `define STATE_EXECUTE          2'h2
 `define STATE_WRITEBACK                2'h3
 
 `define STATE_EXECUTE          2'h2
 `define STATE_WRITEBACK                2'h3
 

-`define INSN_LD_reg_imm8       8'b00xxx110
-`define INSN_HALT              8'b01110110
-`define INSN_LD_HL_reg         8'b01110xxx
-`define INSN_LD_reg_HL         8'b01xxx110
-`define INSN_LD_reg_reg                8'b01xxxxxx
-`define INSN_LD_reg_imm16      8'b00xx0001
-`define INSN_LD_SP_HL          8'b11111001
-`define INSN_PUSH_reg          8'b11xx0101
-`define INSN_POP_reg           8'b11xx0001
-`define INSN_LDH_AC            8'b111x0010     // Either LDH A,(C) or LDH (C),A
-`define INSN_LDx_AHL           8'b001xx010     // LDD/LDI A,(HL) / (HL),A
-`define INSN_ALU8              8'b10xxxxxx     // 10 xxx yyy
-`define INSN_ALU8IMM           8'b11xxx110
-`define INSN_NOP               8'b00000000
-`define INSN_RST               8'b11xxx111
-`define INSN_RET               8'b110x1001     // 1 = RETI, 0 = RET
-`define INSN_RETCC             8'b110xx000
-`define INSN_CALL              8'b11001101
-`define INSN_CALLCC            8'b110xx100     // Not that call/cc.
-`define INSN_JP_imm            8'b11000011
-`define INSN_JPCC_imm          8'b110xx010
-`define INSN_ALU_A             8'b00xxx111
-`define INSN_JP_HL             8'b11101001
-`define INSN_JR_imm            8'b00011000
-`define INSN_JRCC_imm          8'b001xx000
-`define INSN_INCDEC16          8'b00xxx011
-`define INSN_VOP_INTR          8'b11111100     // 0xFC is grabbed by the fetch if there is an interrupt pending.
-`define INSN_DI                        8'b11110011
-`define INSN_EI                        8'b11111011
+`define INSN_LD_reg_imm8       9'b000xxx110
+`define INSN_HALT              9'b001110110
+`define INSN_LD_HL_reg         9'b001110xxx
+`define INSN_LD_reg_HL         9'b001xxx110
+`define INSN_LD_reg_reg                9'b001xxxxxx
+`define INSN_LD_reg_imm16      9'b000xx0001
+`define INSN_LD_SP_HL          9'b011111001
+`define INSN_PUSH_reg          9'b011xx0101
+`define INSN_POP_reg           9'b011xx0001
+`define INSN_LDH_AC            9'b0111x0010    // Either LDH A,(C) or LDH (C),A
+`define INSN_LDx_AHL           9'b0001xx010    // LDD/LDI A,(HL) / (HL),A
+`define INSN_ALU8              9'b010xxxxxx    // 10 xxx yyy
+`define INSN_ALU8IMM           9'b011xxx110
+`define INSN_NOP               9'b000000000
+`define INSN_RST               9'b011xxx111
+`define INSN_RET               9'b0110x1001    // 1 = RETI, 0 = RET
+`define INSN_RETCC             9'b0110xx000
+`define INSN_CALL              9'b011001101
+`define INSN_CALLCC            9'b0110xx100    // Not that call/cc.
+`define INSN_JP_imm            9'b011000011
+`define INSN_JPCC_imm          9'b0110xx010
+`define INSN_ALU_A             9'b000xxx111
+`define INSN_JP_HL             9'b011101001
+`define INSN_JR_imm            9'b000011000
+`define INSN_JRCC_imm          9'b0001xx000
+`define INSN_INCDEC16          9'b000xxx011
+`define INSN_VOP_INTR          9'b011111100    // 0xFC is grabbed by the fetch if there is an interrupt pending.
+`define INSN_DI                        9'b011110011
+`define INSN_EI                        9'b011111011
+`define INSN_INCDEC_HL         9'b00011010x
+`define INSN_INCDEC_reg8       9'b000xxx10x
+`define INSN_LD8M_A            9'b0111x0000    // 1111 for ld A, x; 1110 for ld x, A; bit 1 specifies 16m8 or 8m8
+`define INSN_LD16M_A           9'b0111x1010    // 1111 for ld A, x; 1110 for ld x, A; bit 1 specifies 16m8 or 8m8
+`define INSN_LDBCDE_A          9'b0000xx010
+`define INSN_TWO_BYTE          9'b011001011    // prefix for two-byte opqodes
+`define INSN_ALU_EXT           9'b100xxxxxx
+`define INSN_BIT               9'b101xxxxxx
+`define INSN_RES               9'b110xxxxxx
+`define INSN_SET               9'b111xxxxxx

 
 `define INSN_cc_NZ             2'b00
 `define INSN_cc_Z              2'b01
 
 `define INSN_cc_NZ             2'b00
 `define INSN_cc_Z              2'b01


@@ -107,21 +117,44 @@
 `define INSN_alu_CPL           3'b101
 `define INSN_alu_SCF           3'b110
 `define INSN_alu_CCF           3'b111
 `define INSN_alu_CPL           3'b101
 `define INSN_alu_SCF           3'b110
 `define INSN_alu_CCF           3'b111

+`define INSN_alu_RLC           3'b000
+`define INSN_alu_RRC           3'b001
+`define INSN_alu_RL            3'b010
+`define INSN_alu_RR            3'b011
+`define INSN_alu_DA_SLA                3'b100
+`define INSN_alu_CPL_SRA       3'b101
+`define INSN_alu_SCF_SWAP      3'b110
+`define INSN_alu_CCF_SRL       3'b111

 
 `define EXEC_INC_PC            `_PC <= `_PC + 1;
 `define EXEC_NEXTADDR_PCINC    address <= `_PC + 1;
 `define EXEC_NEWCYCLE          begin newcycle <= 1; rd <= 1; wr <= 0; end
 
 `define EXEC_INC_PC            `_PC <= `_PC + 1;
 `define EXEC_NEXTADDR_PCINC    address <= `_PC + 1;
 `define EXEC_NEWCYCLE          begin newcycle <= 1; rd <= 1; wr <= 0; end

-`define EXEC_WRITE(ad, da)     begin address <= (ad); wdata <= (da); wr <= 1; end end
-`define EXEC_READ(ad)          begin address <= (ad); rd <= 1; end end
+`define EXEC_NEWCYCLE_TWOBYTE  begin newcycle <= 1; rd <= 1; wr <= 0; twobyte <= 1; end
+`ifdef verilator
+       `define EXEC_WRITE(ad, da)      begin address <= (ad); wdata <= (da); wr <= 1; end
+       `define EXEC_READ(ad)           begin address <= (ad); rd <= 1; end
+`else
+       `ifdef isim
+               `define EXEC_WRITE(ad, da)      begin address <= (ad); wdata <= (da); wr <= 1; end
+               `define EXEC_READ(ad)           begin address <= (ad); rd <= 1; end
+       `else
+/* Work around XST's retarded bugs :\ */
+               `define EXEC_WRITE(ad, da)      begin address <= (ad); wdata <= (da); wr <= 1; end end
+               `define EXEC_READ(ad)           begin address <= (ad); rd <= 1; end end
+       `endif
+`endif

 
 module GBZ80Core(
        input clk,
 
 module GBZ80Core(
        input clk,

-       output reg [15:0] busaddress,   /* BUS_* is latched on STATE_FETCH. */
-       inout [7:0] busdata,
-       output reg buswr, output reg busrd,
+       inout [15:0] bus0address,       /* BUS_* is latched on STATE_FETCH. */
+       inout [7:0] bus0data,
+       inout bus0wr, bus0rd,
+       inout [15:0] bus1address,       /* BUS_* is latched on STATE_FETCH. */
+       inout [7:0] bus1data,
+       inout bus1wr, bus1rd,

        input irq, input [7:0] jaddr,
        output reg [1:0] state);
        input irq, input [7:0] jaddr,
        output reg [1:0] state);

-       
+

 //     reg [1:0] state;                                        /* State within this bus cycle (see STATE_*). */
        reg [2:0] cycle;                                        /* Cycle for instructions. */
        
 //     reg [1:0] state;                                        /* State within this bus cycle (see STATE_*). */
        reg [2:0] cycle;                                        /* Cycle for instructions. */
        


@@ -129,31 +162,111 @@ module GBZ80Core(
        
        reg [15:0] address;                             /* Address for the next bus operation. */
        
        
        reg [15:0] address;                             /* Address for the next bus operation. */
        

-       reg [7:0] opcode;                               /* Opcode from the current machine cycle. */
-       
+       reg [8:0] opcode;                               /* Opcode from the current machine cycle. */
+

        reg [7:0] rdata, wdata;         /* Read data from this bus cycle, or write data for the next. */
        reg [7:0] rdata, wdata;         /* Read data from this bus cycle, or write data for the next. */

-       reg rd, wr, newcycle;
+       reg rd, wr, newcycle, twobyte;

        
        reg [7:0] tmp, tmp2;                    /* Generic temporary regs. */
        
        reg [7:0] buswdata;
        
        reg [7:0] tmp, tmp2;                    /* Generic temporary regs. */
        
        reg [7:0] buswdata;

-       assign busdata = buswr ? buswdata : 8'bzzzzzzzz;
+       wire [7:0] busdata;

        
        

-       reg ie, iedelay;
+       reg [15:0] busaddress;
+       reg buswr, busrd;

        
        

+       reg bootstrap_enb;
+       
+       wire bus = ((busaddress[15:8] == 8'h00) && bootstrap_enb) || ((busaddress[15:7] == 9'b111111111) && (busaddress != 16'hFFFF))   /* 0 or 1 depending on which bus */
+               `ifdef isim
+                       || (busaddress === 16'hxxxx) /* To avoid simulator glomulation. */
+               `endif
+                       ;
+               
+       assign bus0address = (bus == 0) ? busaddress : 16'bzzzzzzzzzzzzzzz;
+       assign bus1address = (bus == 1) ? busaddress : 16'bzzzzzzzzzzzzzzz;
+       assign bus0data = ((bus == 0) && buswr) ? buswdata : 8'bzzzzzzzz;
+       assign bus1data = ((bus == 1) && buswr) ? buswdata : 8'bzzzzzzzz;
+       assign busdata = (bus == 0) ? bus0data : bus1data;
+       assign bus0rd = (bus == 0) ? busrd : 1'b0;
+       assign bus1rd = (bus == 1) ? busrd : 1'b0;
+       assign bus0wr = (bus == 0) ? buswr : 1'b0;
+       assign bus1wr = (bus == 1) ? buswr : 1'b0;
+
+       reg ie, iedelay;
+
+       wire [7:0] rlc,rrc,rl,rr,sla,sra,swap,srl;
+       wire [3:0] rlcf,rrcf,rlf,rrf,slaf,sraf,swapf,srlf;
+       wire [7:0] alu_res;
+       wire [3:0] f_res;
+
+       assign rlc   = {tmp[6:0],tmp[7]};
+       assign rlcf  = {(tmp == 0 ? 1'b1 : 1'b0)
+                       ,2'b0,
+                       tmp[7]};
+
+       assign rrc   = {tmp[0],tmp[7:1]};
+       assign rrcf  = {(tmp == 0 ? 1'b1 : 1'b0),
+                       2'b0,
+                       tmp[0]};
+
+       assign rl    = {tmp[6:0],`_F[4]};
+       assign rlf   = {({tmp[6:0],`_F[4]} == 0 ? 1'b1 : 1'b0),
+                       2'b0,
+                       tmp[7]};
+
+       assign rr    = {`_F[4],tmp[7:1]};
+       assign rrf   = {({tmp[4],tmp[7:1]} == 0 ? 1'b1 : 1'b0),
+                       2'b0,
+                       tmp[0]};
+
+       assign sla   = {tmp[6:0],1'b0};
+       assign slaf  = {(tmp[6:0] == 0 ? 1'b1 : 1'b0),
+                       2'b0,
+                       tmp[7]};
+
+       assign sra   = {tmp[7],tmp[7:1]};
+//     assign sraf  = {(tmp[7:1] == 0 ? 1'b1 : 1'b0),2'b0,tmp[0]};   now in assign srlf =
+
+       assign swap  = {tmp[3:0],tmp[7:4]};
+       assign swapf = {(tmp == 1'b0 ? 1'b1 : 1'b0),
+                       3'b0};
+
+       assign srl   = {1'b0,tmp[7:1]};
+       assign srlf  = {(tmp[7:1] == 0 ? 1'b1 : 1'b0),
+                       2'b0,
+                       tmp[0]};
+       assign sraf  = srlf;
+
+       /*  Y U Q  */
+       assign {alu_res,f_res} =
+               opcode[5] ? (
+                       opcode[4] ? (
+                               opcode[3] ? {srl,srlf} : {swap,swapf}
+                       ) : (
+                               opcode[3] ? {sra,sraf} : {sla,slaf}
+                       )
+               ) : (
+                       opcode[4] ? (
+                               opcode[3] ? {rr,rrf} : {rl,rlf}
+                       ) : (
+                               opcode[3] ? {rrc,rrcf} : {rlc,rlcf}
+                       )
+               );
+

        initial begin
        initial begin

-               registers[ 0] <= 0;
-               registers[ 1] <= 0;
-               registers[ 2] <= 0;
-               registers[ 3] <= 0;
-               registers[ 4] <= 0;
-               registers[ 5] <= 0;
-               registers[ 6] <= 0;
-               registers[ 7] <= 0;
-               registers[ 8] <= 0;
-               registers[ 9] <= 0;
-               registers[10] <= 0;
-               registers[11] <= 0;
+               `_A <= 0;
+               `_B <= 0;
+               `_C <= 0;
+               `_D <= 0;
+               `_E <= 0;
+               `_F <= 0;
+               `_H <= 0;
+               `_L <= 0;
+               `_PCH <= 0;
+               `_PCL <= 0;
+               `_SPH <= 0;
+               `_SPL <= 0;

                rd <= 1;
                wr <= 0;
                newcycle <= 1;
                rd <= 1;
                wr <= 0;
                newcycle <= 1;


@@ -167,13 +280,15 @@ module GBZ80Core(
                opcode <= 0;
                state <= `STATE_WRITEBACK;
                cycle <= 0;
                opcode <= 0;
                state <= `STATE_WRITEBACK;
                cycle <= 0;

+               twobyte <= 0;
+               bootstrap_enb <= 1;

        end
 
        end
 

-       always @(posedge clk)
+       always @(negedge clk)   /* Set things up at the negedge to prepare for the posedge. */

                case (state)
                `STATE_FETCH: begin
                        if (newcycle) begin
                case (state)
                `STATE_FETCH: begin
                        if (newcycle) begin

-                               busaddress <= {registers[`REG_PCH], registers[`REG_PCL]};
+                               busaddress <= `_PC;

                                buswr <= 0;
                                busrd <= 1;
                        end else begin
                                buswr <= 0;
                                busrd <= 1;
                        end else begin


@@ -183,27 +298,39 @@ module GBZ80Core(
                                if (wr)
                                        buswdata <= wdata;
                        end
                                if (wr)
                                        buswdata <= wdata;
                        end

+               end
+               `STATE_DECODE: begin    /* Make sure this only happens for one clock. */
+                       buswr <= 0;
+                       busrd <= 0;
+               end
+               endcase
+       
+       always @(posedge clk)
+               case (state)
+               `STATE_FETCH: begin
+                       /* Things are set up in negedge so that something looking on posedge will get his shit. */

                        state <= `STATE_DECODE;
                end
                `STATE_DECODE: begin
                        if (newcycle) begin
                        state <= `STATE_DECODE;
                end
                `STATE_DECODE: begin
                        if (newcycle) begin

-                               if (ie && irq)
+                               if (twobyte) begin
+                                       opcode <= {1'b1,busdata};
+                                       twobyte <= 0;
+                               end else if (ie && irq)

                                        opcode <= `INSN_VOP_INTR;
                                else
                                        opcode <= `INSN_VOP_INTR;
                                else

-                                       opcode <= busdata;
-                               rdata <= busdata;
+                                       opcode <= {1'b0,busdata};

                                newcycle <= 0;
                                newcycle <= 0;

+                               rdata <= busdata;

                                cycle <= 0;
                        end else begin
                                cycle <= 0;
                        end else begin

-                               if (rd) rdata <= busdata;
+                               if (rd) rdata <= busdata;       /* Still valid because peripherals are now expected to keep it held valid. */

                                cycle <= cycle + 1;
                        end
                        if (iedelay) begin
                                ie <= 1;
                                iedelay <= 0;
                        end
                                cycle <= cycle + 1;
                        end
                        if (iedelay) begin
                                ie <= 1;
                                iedelay <= 0;
                        end

-                       buswr <= 0;
-                       busrd <= 0;

                        wr <= 0;
                        rd <= 0;
                        address <= 16'bxxxxxxxxxxxxxxxx;        // Make it obvious if something of type has happened.
                        wr <= 0;
                        rd <= 0;
                        address <= 16'bxxxxxxxxxxxxxxxx;        // Make it obvious if something of type has happened.


@@ -211,6 +338,8 @@ module GBZ80Core(
                        state <= `STATE_EXECUTE;
                end
                `STATE_EXECUTE: begin
                        state <= `STATE_EXECUTE;
                end
                `STATE_EXECUTE: begin

+                       if (opcode[7:0] === 8'bxxxxxxxx)
+                               $stop;

                        casex (opcode)
                        `define EXECUTE
                        `include "allinsns.v"
                        casex (opcode)
                        `define EXECUTE
                        `include "allinsns.v"