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Added support for some register indirect addressing modes. Also added documentation comments and did some general cleanup

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This commit is contained in:
(Tim) Efthimis Kritikos 2023-02-11 20:27:28 +00:00
parent 85bf886223
commit 0901af23db
3 changed files with 164 additions and 39 deletions
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6
cpu/proc_state_def.v
View File

@ -12,6 +12,12 @@
`define PROC_DE_LOAD_16_EXTRA_FETCH_SET 4'b0110
`define PROC_DE_LOAD_16_EXTRA_FETCH 4'b0111
/*MEM/IO READ*/
`define RPOC_MEMIO_READ 4'b1100
`define PROC_MEMIO_SETADDR 4'b1101
`define PROC_MEMIO_GET_ALIGNED_DATA 4'b1110 /* :) */
`define PROC_MEMIO_GET_UNALIGNED_DATA 4'b1010 /* :( */
/*EXECUTE STATE*/
`define PROC_EX_STATE_ENTRY 4'b1000
`define PROC_EX_STATE_EXIT 4'b1001

175
cpu/processor.v
View File

@ -24,6 +24,9 @@ reg [15:0] CIR;
reg [15:0] PARAM1;
reg [15:0] PARAM2;
reg unaligned_access;
reg [1:0]IN_MOD;
reg [2:0]IN_RM;
reg Wbit;
// Execution units
reg [1:0] in1_sel;
@ -44,6 +47,7 @@ always @(negedge reset) begin
@(posedge reset)
@(negedge clock);
state=`PROC_IF_STATE_ENTRY;
IN_MOD=2'b11;
end
end
@ -80,12 +84,13 @@ wire [15:0] ALU_1B;
wire [15:0] ALU_1O;
reg [`ALU_OP_BITS-1:0]ALU_1OP;
reg ALU_1OE;
//reg [15:0] temp_out;
ALU ALU(ALU_1A,ALU_1B,ALU_1OE,ALU_1O,ALU_1OP);
/*** Processor stages ***/
`define invalid_instruction state=`PROC_IF_STATE_ENTRY;ERROR=1;
`define invalid_instruction state=`PROC_IF_STATE_ENTRY;ERROR=1;IN_MOD=2'b11;
`define start_aligning_instruction if(unaligned_access==0)begin ProgCount=ProgCount+1; external_address_bus <= ProgCount; end /*we normally don't advance PC in case of singly byte unaligning instructions leasving us with two instructions in one read so do that here*/
`define start_unaligning_instruction unaligned_access=~unaligned_access;
always @(negedge clock) begin
case(state)
@ -118,6 +123,10 @@ always @(negedge clock) begin
external_address_bus = ProgCount;
state=`PROC_DE_LOAD_16_EXTRA_FETCH;
end
`PROC_MEMIO_SETADDR:begin
external_address_bus = {1'b0,reg_read_data[15:1]};
state=reg_read_data[0:0]?`PROC_MEMIO_GET_UNALIGNED_DATA:`PROC_MEMIO_GET_ALIGNED_DATA;
end
endcase
end
@ -139,6 +148,7 @@ always @(posedge clock) begin
external_address_bus <= ProgCount;
state=`PROC_IF_STATE_EXTRA_FETCH;
end
/* 0 0 0 0 0 0 0 0 | 0 0 0 0 0 0 0 0 | 0 0 0 0 0 0 0 0 | 0 0 0 0 0 0 0 0 */
/* AFTER THE IF STAGE WE HAVE THE FRIST BYTE OF THE
* INSTRUCTION ADN THE ONE FOLLOWING, ALLIGNED CORRECTLY TO
* CIR */
@ -148,7 +158,13 @@ always @(posedge clock) begin
/* ADD, ... */
if ( CIR[9:9] == 0 )begin
/* Add Immediate word/byte to accumulator */
unaligned_access=~unaligned_access;
/* 0 0 0 0 0 1 0 W | DATA | DATA if W |*/
Wbit=CIR[8:8];
if(Wbit)
`start_unaligning_instruction
else
`start_aligning_instruction
IN_MOD=2'b11;
in1_sel=2'b00;
in2_sel=2'b01;
out_sel=2'b11;
@ -171,10 +187,9 @@ always @(posedge clock) begin
case (CIR[5:3])
3'b000 : begin
/* Add Immediate word/byte to register/memory */
if(unaligned_access==0)begin
ProgCount=ProgCount+1;
external_address_bus <= ProgCount;
end
/* 1 0 0 0 0 0 S W | MOD 0 0 0 R/M | < DISP LO > | < DISP HI > | DATA | DATA if W | */
`start_aligning_instruction
IN_MOD=2'b11;
in1_sel=2'b00;
in2_sel=2'b01;
out_sel=CIR[7:6];
@ -197,12 +212,14 @@ always @(posedge clock) begin
end
6'b101100,
6'b101101:begin
/*Move Immediate byte to register*/
if(unaligned_access==0)begin
ProgCount=ProgCount+1;
external_address_bus <= ProgCount;
end
unaligned_access=~unaligned_access;
/* MOV - Move Immediate byte to register */
/* 1 0 1 1 W REG | DATA | DATA if W |*/
Wbit=CIR[11:11];
if(Wbit)
`start_unaligning_instruction
else
`start_aligning_instruction
IN_MOD=2'b11;
in1_sel=2'b00;
in2_sel=2'b00;
out_sel=2'b11;
@ -215,8 +232,13 @@ always @(posedge clock) begin
end
6'b101110,
6'b101111 : begin
/*Move Immediate word to register*/
unaligned_access=~unaligned_access;
/*MOV - Move Immediate word to register*/
Wbit=CIR[11:11];
if(Wbit)
`start_unaligning_instruction
else
`start_aligning_instruction
IN_MOD=2'b11;
in1_sel=2'b00;
in2_sel=2'b00;
out_sel=2'b11;
@ -226,15 +248,52 @@ always @(posedge clock) begin
PARAM2=0;
state=`PROC_DE_LOAD_16_PARAM;
end
6'b100010 : begin
/* MOV - Reg/Mem to/from register */
/* 1 0 0 0 1 0 D W | MOD REG REG | < DISP LO > | < DISP HI > |*/
`start_aligning_instruction
IN_MOD=CIR[7:6];
IN_RM=CIR[2:0];
Wbit=CIR[8:8];
if(CIR[9:9] == 1)begin
/* to reg */
IN_MOD=CIR[7:6];
if(IN_MOD==2'b11)begin
in1_sel=2'b01;
reg_read_addr=CIR[2:0];
end else begin
in1_sel=2'b00;
end
in2_sel=2'b00;
out_sel=2'b11;
reg_write_addr={CIR[8:8],CIR[5:3]};
end else begin
`invalid_instruction
end
ALU_1OE=0;
ALU_1OP=`ALU_OP_ADD;
PARAM2=0;
state=`PROC_DE_LOAD_16_PARAM;
if ( IN_MOD == 2'b11 )
state=`PROC_EX_STATE_ENTRY;
else
state=`RPOC_MEMIO_READ;
end
6'b010000,//INC
6'b010001,//INC
6'b010010,//DEC
6'b010011:begin//DEC
/*INC/DEC Register*/
unaligned_access=~unaligned_access;
/* DEC - Decrement Register */
/* | 0 1 0 0 1 REG | */
/* INC - Increment Register */
/* | 0 1 0 0 0 REG | */
`start_unaligning_instruction
in1_sel=2'b01;
in2_sel=2'b00;
out_sel=2'b11;
IN_MOD=2'b11;
PARAM2=1;
reg_read_addr={1'b1,CIR[10:8]};
reg_write_addr={1'b1,CIR[10:8]};
@ -251,13 +310,12 @@ always @(posedge clock) begin
if (CIR[9:9] == 1 ) begin
case (CIR[5:3])
3'b000 :begin
/* Increment Register or Memmory */
if(unaligned_access==0)begin
ProgCount=ProgCount+1;
external_address_bus <= ProgCount;
end
in1_sel=2'b00;
in2_sel=2'b01;
/* INC - Register/Memory */
/* 1 1 1 1 1 1 1 W | MOD 0 0 0 R/M | < DISP LO> | < DISP HI> */
`start_aligning_instruction
IN_MOD=CIR[7:6];
in1_sel=2'b00;/* number 1 */
in2_sel=(CIR[7:6]==2'b11)? 2'b01 : 2'b00;
out_sel=CIR[7:6];
PARAM1=1;
reg_read_addr={1'b0,CIR[2:0]};
@ -265,7 +323,10 @@ always @(posedge clock) begin
reg_read_oe=0;
ALU_1OE=0;
ALU_1OP=`ALU_OP_ADD;
if ( CIR[7:6] == 2'b11 )
state=`PROC_EX_STATE_ENTRY;
else
state=`RPOC_MEMIO_READ;
end
default:begin
`invalid_instruction
@ -279,8 +340,10 @@ always @(posedge clock) begin
/*HLT, CMC, TEST, NOT, NEG, MUL, IMUL, .... */
case (CIR[9:8])
2'b00:begin
/* HLT*/
unaligned_access=~unaligned_access;
/* HLT - Halt */
/* 1 1 1 1 0 1 0 0 | */
`start_unaligning_instruction
IN_MOD=2'b11;
HALT=1;
state=`PROC_HALT_STATE;
end
@ -311,6 +374,66 @@ always @(posedge clock) begin
PARAM1[15:8] = external_data_bus[15:8];
state=`PROC_EX_STATE_ENTRY;
end
`RPOC_MEMIO_READ:begin
/*Decode MOD R/M, read the data and place it to PARAM1*/
case (IN_RM)
3'b000:begin
/*[BX]+[SI]*/
`invalid_instruction
end
3'b001:begin
/*[BX]+[SI]*/
`invalid_instruction
end
3'b010:begin
/*[BP]+[SI]*/
`invalid_instruction
end
3'b011:begin
/*[BP]+[DI]*/
`invalid_instruction
end
3'b100:begin
/*[SI]*/
reg_read_addr=4'b1110;
reg_read_oe=0;
state=`PROC_MEMIO_SETADDR;
end
3'b101:begin
/*[DI]*/
reg_read_addr=4'b1111;
reg_read_oe=0;
state=`PROC_MEMIO_SETADDR;
end
3'b110:begin
/*d16 */
`invalid_instruction
end
3'b111:begin
/*[BX]*/
reg_read_addr=4'b1011;
reg_read_oe=0;
state=`PROC_MEMIO_SETADDR;
end
endcase
if(IN_MOD!=2'b00)begin
/*Actually check if 01 and add the 8bits or if 10 add the 16bits ....*/
`invalid_instruction;
end
end
`PROC_MEMIO_GET_ALIGNED_DATA:begin
PARAM1=(Wbit==1)? external_data_bus : {8'b00000000,external_data_bus[15:8]} ;
state=`PROC_EX_STATE_ENTRY;
end
`PROC_MEMIO_GET_UNALIGNED_DATA:begin
if(Wbit==1) begin
`invalid_instruction //easy to implement, get the other byte from the next address
end else begin
PARAM1={8'b00000000,external_data_bus[7:0]};
state=`PROC_EX_STATE_ENTRY;
end
end
`PROC_EX_STATE_ENTRY:begin
reg_write_data=ALU_1O;
state=`PROC_EX_STATE_EXIT;

6
cpu/registers.v
View File

@ -18,7 +18,6 @@ assign read_port1_data = !read_port1_oe ?
`ifdef DEBUG_REG_WRITES
string debug_name;
logic[15:0] debug_value;
`endif
always @(negedge write_port1_we) begin
@ -44,7 +43,6 @@ always @(negedge write_port1_we) begin
2'b10: debug_name="si";
2'b11: debug_name="di";
endcase
debug_value=registers[write_port1_addr[2:0]];
end else begin
case(write_port1_addr[1:0])
2'b00: debug_name="ax";
@ -52,11 +50,9 @@ always @(negedge write_port1_we) begin
2'b10: debug_name="dx";
2'b11: debug_name="bx";
endcase
debug_value=registers[write_port1_addr[2:0]];
end
$display("register %%%s update to $0x%04x",debug_name,debug_value);
$display("register %%%s update to $0x%04x",debug_name,registers[write_port1_addr[2:0]]);
`endif
end
endmodule