Dual bus processor
[fpgaboy.git] / GBZ80Core.v
CommitLineData
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1`define REG_A 0
2`define REG_B 1
3`define REG_C 2
4`define REG_D 3
5`define REG_E 4
6`define REG_F 5
7`define REG_H 6
8`define REG_L 7
9`define REG_SPH 8
10`define REG_SPL 9
11`define REG_PCH 10
12`define REG_PCL 11
2f55f809 13
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14`define _A registers[`REG_A]
15`define _B registers[`REG_B]
16`define _C registers[`REG_C]
17`define _D registers[`REG_D]
18`define _E registers[`REG_E]
19`define _F registers[`REG_F]
20`define _H registers[`REG_H]
21`define _L registers[`REG_L]
22`define _SPH registers[`REG_SPH]
23`define _SPL registers[`REG_SPL]
24`define _PCH registers[`REG_PCH]
25`define _PCL registers[`REG_PCL]
26`define _AF {`_A, `_F}
27`define _BC {`_B, `_C}
28`define _DE {`_D, `_E}
29`define _HL {`_H, `_L}
30`define _SP {`_SPH, `_SPL}
31`define _PC {`_PCH, `_PCL}
32
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33`define FLAG_Z 8'b10000000
34`define FLAG_N 8'b01000000
35`define FLAG_H 8'b00100000
36`define FLAG_C 8'b00010000
2f55f809 37
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38`define STATE_FETCH 2'h0
39`define STATE_DECODE 2'h1
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40`define STATE_EXECUTE 2'h2
41`define STATE_WRITEBACK 2'h3
42
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43`define INSN_LD_reg_imm8 9'b000xxx110
44`define INSN_HALT 9'b001110110
45`define INSN_LD_HL_reg 9'b001110xxx
46`define INSN_LD_reg_HL 9'b001xxx110
47`define INSN_LD_reg_reg 9'b001xxxxxx
48`define INSN_LD_reg_imm16 9'b000xx0001
49`define INSN_LD_SP_HL 9'b011111001
50`define INSN_PUSH_reg 9'b011xx0101
51`define INSN_POP_reg 9'b011xx0001
52`define INSN_LDH_AC 9'b0111x0010 // Either LDH A,(C) or LDH (C),A
53`define INSN_LDx_AHL 9'b0001xx010 // LDD/LDI A,(HL) / (HL),A
54`define INSN_ALU8 9'b010xxxxxx // 10 xxx yyy
55`define INSN_ALU8IMM 9'b011xxx110
56`define INSN_NOP 9'b000000000
57`define INSN_RST 9'b011xxx111
58`define INSN_RET 9'b0110x1001 // 1 = RETI, 0 = RET
59`define INSN_RETCC 9'b0110xx000
60`define INSN_CALL 9'b011001101
61`define INSN_CALLCC 9'b0110xx100 // Not that call/cc.
62`define INSN_JP_imm 9'b011000011
63`define INSN_JPCC_imm 9'b0110xx010
64`define INSN_ALU_A 9'b000xxx111
65`define INSN_JP_HL 9'b011101001
66`define INSN_JR_imm 9'b000011000
67`define INSN_JRCC_imm 9'b0001xx000
68`define INSN_INCDEC16 9'b000xxx011
69`define INSN_VOP_INTR 9'b011111100 // 0xFC is grabbed by the fetch if there is an interrupt pending.
70`define INSN_DI 9'b011110011
71`define INSN_EI 9'b011111011
72`define INSN_INCDEC_HL 9'b00011010x
73`define INSN_INCDEC_reg8 9'b000xxx10x
74`define INSN_LD8M_A 9'b0111x0000 // 1111 for ld A, x; 1110 for ld x, A; bit 1 specifies 16m8 or 8m8
75`define INSN_LD16M_A 9'b0111x1010 // 1111 for ld A, x; 1110 for ld x, A; bit 1 specifies 16m8 or 8m8
76`define INSN_LDBCDE_A 9'b0000xx010
77`define INSN_TWO_BYTE 9'b011001011 // prefix for two-byte opqodes
78`define INSN_ALU_EXT 9'b100xxxxxx
79`define INSN_BIT 9'b101xxxxxx
80`define INSN_RES 9'b110xxxxxx
81`define INSN_SET 9'b111xxxxxx
a85b19a7 82
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83`define INSN_cc_NZ 2'b00
84`define INSN_cc_Z 2'b01
85`define INSN_cc_NC 2'b10
86`define INSN_cc_C 2'b11
fa136d63 87
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88`define INSN_reg_A 3'b111
89`define INSN_reg_B 3'b000
90`define INSN_reg_C 3'b001
91`define INSN_reg_D 3'b010
92`define INSN_reg_E 3'b011
93`define INSN_reg_H 3'b100
94`define INSN_reg_L 3'b101
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95`define INSN_reg_dHL 3'b110
96`define INSN_reg16_BC 2'b00
97`define INSN_reg16_DE 2'b01
98`define INSN_reg16_HL 2'b10
99`define INSN_reg16_SP 2'b11
100`define INSN_stack_AF 2'b11
101`define INSN_stack_BC 2'b00
102`define INSN_stack_DE 2'b01
103`define INSN_stack_HL 2'b10
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104`define INSN_alu_ADD 3'b000
105`define INSN_alu_ADC 3'b001
106`define INSN_alu_SUB 3'b010
107`define INSN_alu_SBC 3'b011
108`define INSN_alu_AND 3'b100
109`define INSN_alu_XOR 3'b101
110`define INSN_alu_OR 3'b110
111`define INSN_alu_CP 3'b111 // Oh lawd, is dat some CP?
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112`define INSN_alu_RLCA 3'b000
113`define INSN_alu_RRCA 3'b001
114`define INSN_alu_RLA 3'b010
115`define INSN_alu_RRA 3'b011
116`define INSN_alu_DAA 3'b100
117`define INSN_alu_CPL 3'b101
118`define INSN_alu_SCF 3'b110
119`define INSN_alu_CCF 3'b111
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120`define INSN_alu_RLC 3'b000
121`define INSN_alu_RRC 3'b001
122`define INSN_alu_RL 3'b010
123`define INSN_alu_RR 3'b011
124`define INSN_alu_DA_SLA 3'b100
125`define INSN_alu_CPL_SRA 3'b101
126`define INSN_alu_SCF_SWAP 3'b110
127`define INSN_alu_CCF_SRL 3'b111
94522011 128
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129`define EXEC_INC_PC `_PC <= `_PC + 1;
130`define EXEC_NEXTADDR_PCINC address <= `_PC + 1;
131`define EXEC_NEWCYCLE begin newcycle <= 1; rd <= 1; wr <= 0; end
decafd62 132`define EXEC_NEWCYCLE_TWOBYTE begin newcycle <= 1; rd <= 1; wr <= 0; twobyte <= 1; end
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133`ifdef verilator
134 `define EXEC_WRITE(ad, da) begin address <= (ad); wdata <= (da); wr <= 1; end
135 `define EXEC_READ(ad) begin address <= (ad); rd <= 1; end
136`else
137 `ifdef isim
138 `define EXEC_WRITE(ad, da) begin address <= (ad); wdata <= (da); wr <= 1; end
139 `define EXEC_READ(ad) begin address <= (ad); rd <= 1; end
140 `else
141/* Work around XST's retarded bugs :\ */
142 `define EXEC_WRITE(ad, da) begin address <= (ad); wdata <= (da); wr <= 1; end end
143 `define EXEC_READ(ad) begin address <= (ad); rd <= 1; end end
144 `endif
145`endif
5509558d 146
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147module GBZ80Core(
148 input clk,
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149 inout [15:0] bus0address, /* BUS_* is latched on STATE_FETCH. */
150 inout [7:0] bus0data,
151 inout bus0wr, bus0rd,
152 inout [15:0] bus1address, /* BUS_* is latched on STATE_FETCH. */
153 inout [7:0] bus1data,
154 inout bus1wr, bus1rd,
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155 input irq, input [7:0] jaddr,
156 output reg [1:0] state);
decafd62 157
6c46357c 158// reg [1:0] state; /* State within this bus cycle (see STATE_*). */
9c834ff2 159 reg [2:0] cycle; /* Cycle for instructions. */
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160
161 reg [7:0] registers[11:0];
162
163 reg [15:0] address; /* Address for the next bus operation. */
164
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165 reg [8:0] opcode; /* Opcode from the current machine cycle. */
166
2f55f809 167 reg [7:0] rdata, wdata; /* Read data from this bus cycle, or write data for the next. */
decafd62 168 reg rd, wr, newcycle, twobyte;
2f55f809 169
ef6fbe31 170 reg [7:0] tmp, tmp2; /* Generic temporary regs. */
b85870e0 171
2f55f809 172 reg [7:0] buswdata;
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173 wire [7:0] busdata;
174
175 reg [15:0] busaddress;
176 reg buswr, busrd;
177
178 reg bootstrap_enb;
179
180 wire bus = ((busaddress[15:8] == 8'h00) && bootstrap_enb) || ((busaddress[15:7] == 9'b111111111) && (busaddress != 16'hFFFF)); /* 0 or 1 depending on which bus */
181
182 assign bus0address = (bus == 0) ? busaddress : 16'bzzzzzzzzzzzzzzz;
183 assign bus1address = (bus == 1) ? busaddress : 16'bzzzzzzzzzzzzzzz;
184 assign bus0data = ((bus == 0) && buswr) ? buswdata : 8'bzzzzzzzz;
185 assign bus1data = ((bus == 1) && buswr) ? buswdata : 8'bzzzzzzzz;
186 assign busdata = (bus == 0) ? bus0data : bus1data;
187 assign bus0rd = (bus == 0) ? busrd : 1'bz;
188 assign bus1rd = (bus == 1) ? busrd : 1'bz;
189 assign bus0wr = (bus == 0) ? buswr : 1'bz;
190 assign bus1wr = (bus == 1) ? buswr : 1'bz;
decafd62 191
eb0f2fe1 192 reg ie, iedelay;
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193
194 wire [7:0] rlc,rrc,rl,rr,sla,sra,swap,srl;
195 wire [3:0] rlcf,rrcf,rlf,rrf,slaf,sraf,swapf,srlf;
196 wire [7:0] alu_res;
197 wire [3:0] f_res;
198
199 assign rlc = {tmp[6:0],tmp[7]};
200 assign rlcf = {(tmp == 0 ? 1'b1 : 1'b0)
201 ,2'b0,
202 tmp[7]};
203
204 assign rrc = {tmp[0],tmp[7:1]};
205 assign rrcf = {(tmp == 0 ? 1'b1 : 1'b0),
206 2'b0,
207 tmp[0]};
208
209 assign rl = {tmp[6:0],`_F[4]};
210 assign rlf = {({tmp[6:0],`_F[4]} == 0 ? 1'b1 : 1'b0),
211 2'b0,
212 tmp[7]};
213
214 assign rr = {`_F[4],tmp[7:1]};
215 assign rrf = {({tmp[4],tmp[7:1]} == 0 ? 1'b1 : 1'b0),
216 2'b0,
217 tmp[0]};
218
e7fb589a 219 assign sla = {tmp[6:0],1'b0};
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220 assign slaf = {(tmp[6:0] == 0 ? 1'b1 : 1'b0),
221 2'b0,
222 tmp[7]};
223
224 assign sra = {tmp[7],tmp[7:1]};
225// assign sraf = {(tmp[7:1] == 0 ? 1'b1 : 1'b0),2'b0,tmp[0]}; now in assign srlf =
226
227 assign swap = {tmp[3:0],tmp[7:4]};
e7fb589a 228 assign swapf = {(tmp == 1'b0 ? 1'b1 : 1'b0),
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229 3'b0};
230
e7fb589a 231 assign srl = {1'b0,tmp[7:1]};
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232 assign srlf = {(tmp[7:1] == 0 ? 1'b1 : 1'b0),
233 2'b0,
234 tmp[0]};
235 assign sraf = srlf;
236
237 /* Y U Q */
238 assign {alu_res,f_res} =
239 opcode[5] ? (
240 opcode[4] ? (
241 opcode[3] ? {srl,srlf} : {swap,swapf}
242 ) : (
243 opcode[3] ? {sra,sraf} : {sla,slaf}
244 )
245 ) : (
246 opcode[4] ? (
247 opcode[3] ? {rr,rrf} : {rl,rlf}
248 ) : (
249 opcode[3] ? {rrc,rrcf} : {rlc,rlcf}
250 )
251 );
252
2f55f809 253 initial begin
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254 `_A <= 0;
255 `_B <= 0;
256 `_C <= 0;
257 `_D <= 0;
258 `_E <= 0;
259 `_F <= 0;
260 `_H <= 0;
261 `_L <= 0;
262 `_PCH <= 0;
263 `_PCL <= 0;
264 `_SPH <= 0;
265 `_SPL <= 0;
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266 rd <= 1;
267 wr <= 0;
268 newcycle <= 1;
269 state <= 0;
270 cycle <= 0;
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271 busrd <= 0;
272 buswr <= 0;
273 busaddress <= 0;
9c834ff2 274 ie <= 0;
f8db6448 275 iedelay <= 0;
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276 opcode <= 0;
277 state <= `STATE_WRITEBACK;
278 cycle <= 0;
decafd62 279 twobyte <= 0;
91c74a3f 280 bootstrap_enb <= 1;
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281 end
282
283 always @(posedge clk)
284 case (state)
285 `STATE_FETCH: begin
2e642f1f 286 if (newcycle) begin
decafd62 287 busaddress <= `_PC;
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288 buswr <= 0;
289 busrd <= 1;
290 end else begin
2f55f809 291 busaddress <= address;
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292 buswr <= wr;
293 busrd <= rd;
294 if (wr)
295 buswdata <= wdata;
296 end
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297 state <= `STATE_DECODE;
298 end
299 `STATE_DECODE: begin
300 if (newcycle) begin
decafd62 301 if (twobyte) begin
e7fb589a 302 opcode <= {1'b1,busdata};
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303 twobyte <= 0;
304 end else if (ie && irq)
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305 opcode <= `INSN_VOP_INTR;
306 else
e7fb589a 307 opcode <= {1'b0,busdata};
2f55f809 308 rdata <= busdata;
b85870e0 309 newcycle <= 0;
2f55f809 310 cycle <= 0;
2e642f1f 311 end else begin
2f55f809 312 if (rd) rdata <= busdata;
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313 cycle <= cycle + 1;
314 end
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315 if (iedelay) begin
316 ie <= 1;
317 iedelay <= 0;
318 end
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319 buswr <= 0;
320 busrd <= 0;
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321 wr <= 0;
322 rd <= 0;
323 address <= 16'bxxxxxxxxxxxxxxxx; // Make it obvious if something of type has happened.
324 wdata <= 8'bxxxxxxxx;
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325 state <= `STATE_EXECUTE;
326 end
327 `STATE_EXECUTE: begin
2f55f809 328 casex (opcode)
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329 `define EXECUTE
330 `include "allinsns.v"
331 `undef EXECUTE
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332 default:
333 $stop;
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334 endcase
335 state <= `STATE_WRITEBACK;
336 end
337 `STATE_WRITEBACK: begin
338 casex (opcode)
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339 `define WRITEBACK
340 `include "allinsns.v"
341 `undef WRITEBACK
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342 default:
343 $stop;
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344 endcase
345 state <= `STATE_FETCH;
346 end
347 endcase
348endmodule
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