ELEC40006-P1-CW/DECODE.v

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module DECODE
(
input [15:0] instr,
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input EXEC1,
input EXEC2,
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input COND_result,
output R0_count,
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output R0_en,
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output R1_en,
output R2_en,
output R3_en,
output R4_en,
output R5_en,
output R6_en,
output R7_en,
output [2:0] s1,
output [2:0] s2,
output [2:0] s3,
output s4,
output RAMd_wren,
output RAMd_en,
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output RAMi_en,
output ALU_en,
output E2,
output stack_en,
output stack_rst,
output stack_rw
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);
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wire msb = instr[15]; //MSB of the instruction word
wire ls = instr[14]; //LOAD or STORE bit
wire [2:0] Rls = instr[13:11]; //Register in the LOAD/STORE operation
wire [10:0] addr = instr[10:0]; //Memory address in the LOAD/STORE operation
wire [5:0] op = instr[14:9]; //Opcode in regular instructions
wire [2:0] Rd = instr[8:6]; //Destination register in command
wire [2:0] Rs1 = instr[5:3]; //Source register 1 in command
wire [2:0] Rs2 = instr[2:0]; //Source register 2 in command
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//Different opcodes (refer to documentation):
wire LOAD = msb & ~ls;
wire STORE = msb & ls;
wire UJMP = ~op[5] & ~op[4] & ~op[3] & ~op[2];
wire JMP = (~op[5] & ~op[4] & ~op[3] & op[2]) | (~op[5] & ~op[4] & op[3] & ~op[2]);
wire MUL = ~op[5] & op[4] & op[3] & op[2] & ~op[1] & ~op[0];
wire MLA = ~op[5] & op[4] & op[3] & op[2] & ~op[1] & op[0];
wire MLS = ~op[5] & op[4] & op[3] & op[2] & op[1] & ~op[0];
wire PSH = op[5] & ~op[4] & op[3] & ~op[2] & ~op[1] & ~op[0];
wire POP = op[5] & ~op[4] & op[3] & ~op[2] & ~op[1] & op[0];
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wire NOP = op[5] & op[4] & op[3] & op[2] & op[1] & ~op[0];
wire STP = op[5] & op[4] & op[3] & op[2] & op[1] & op[0];
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assign R0_count = EXEC1 & (~(UJMP | JMP | STP));
assign R0_en = EXEC1 & (~(STORE | NOP | STP) & ~Rd[2] & ~Rd[1] & ~Rd[0] | UJMP | JMP & COND_result) | EXEC2 & LOAD & ~Rls[2] & ~Rls[1] & ~Rls[0] | EXEC2 & (MUL | MLA | MLS | POP) & ~Rd[2] & ~Rd[1] & ~Rd[0];
assign R1_en = EXEC1 & ~(UJMP | JMP | STORE | LOAD | MUL | MLA | MLS | NOP | STP | POP) & ~Rd[2] & ~Rd[1] & Rd[0] | EXEC2 & LOAD & ~Rls[2] & ~Rls[1] & Rls[0] | EXEC2 & (MUL | MLA | MLS | POP) & ~Rd[2] & ~Rd[1] & Rd[0];
assign R2_en = EXEC1 & ~(UJMP | JMP | STORE | LOAD | MUL | MLA | MLS | NOP | STP | POP) & ~Rd[2] & Rd[1] & ~Rd[0] | EXEC2 & LOAD & ~Rls[2] & Rls[1] & ~Rls[0] | EXEC2 & (MUL | MLA | MLS | POP) & ~Rd[2] & Rd[1] & ~Rd[0];
assign R3_en = EXEC1 & ~(UJMP | JMP | STORE | LOAD | MUL | MLA | MLS | NOP | STP | POP) & ~Rd[2] & Rd[1] & Rd[0] | EXEC2 & LOAD & ~Rls[2] & Rls[1] & Rls[0] | EXEC2 & (MUL | MLA | MLS | POP) & ~Rd[2] & Rd[1] & Rd[0];
assign R4_en = EXEC1 & ~(UJMP | JMP | STORE | LOAD | MUL | MLA | MLS | NOP | STP | POP) & Rd[2] & ~Rd[1] & ~Rd[0] | EXEC2 & LOAD & Rls[2] & ~Rls[1] & ~Rls[0] | EXEC2 & (MUL | MLA | MLS | POP) & Rd[2] & ~Rd[1] & ~Rd[0];
assign R5_en = EXEC1 & ~(UJMP | JMP | STORE | LOAD | MUL | MLA | MLS | NOP | STP | POP) & Rd[2] & ~Rd[1] & Rd[0] | EXEC2 & LOAD & Rls[2] & ~Rls[1] & Rls[0] | EXEC2 & (MUL | MLA | MLS | POP) & Rd[2] & ~Rd[1] & Rd[0];
assign R6_en = EXEC1 & ~(UJMP | JMP | STORE | LOAD | MUL | MLA | MLS | NOP | STP | POP) & Rd[2] & Rd[1] & ~Rd[0] | EXEC2 & LOAD & Rls[2] & Rls[1] & ~Rls[0] | EXEC2 & (MUL | MLA | MLS | POP) & Rd[2] & Rd[1] & ~Rd[0];
assign R7_en = EXEC1 & ~(UJMP | JMP | STORE | LOAD | MUL | MLA | MLS | NOP | STP | POP) & Rd[2] & Rd[1] & Rd[0] | EXEC2 & LOAD & Rls[2] & Rls[1] & Rls[0] | EXEC2 & (MUL | MLA | MLS | POP) & Rd[2] & Rd[1] & Rd[0];
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assign s1[2] = EXEC1 & ((~(UJMP | JMP | STORE | LOAD | NOP | STP | PSH | POP) & Rs1[2]) | (STORE & Rls[2]) | (PSH & Rs1[2]));
assign s1[1] = EXEC1 & ((~(UJMP | JMP | STORE | LOAD | NOP | STP | PSH | POP) & Rs1[1]) | (STORE & Rls[1]) | (PSH & Rs1[1]));
assign s1[0] = EXEC1 & ((~(UJMP | JMP | STORE | LOAD | NOP | STP | PSH | POP) & Rs1[0]) | (STORE & Rls[0]) | (PSH & Rs1[0]));
assign s2[2] = EXEC1 & ((~(UJMP | JMP | STORE | LOAD | NOP | STP | PSH | POP)) & Rs2[2]);
assign s2[1] = EXEC1 & ((~(UJMP | JMP | STORE | LOAD | NOP | STP | PSH | POP)) & Rs2[1]);
assign s2[0] = EXEC1 & ((~(UJMP | JMP | STORE | LOAD | NOP | STP | PSH | POP)) & Rs2[0]);
assign s3[2] = EXEC1 & ((~(UJMP | JMP | STORE | LOAD | NOP | STP | PSH | POP)) & Rd[2]);
assign s3[1] = EXEC1 & ((~(UJMP | JMP | STORE | LOAD | NOP | STP | PSH | POP)) & Rd[1]);
assign s3[0] = EXEC1 & ((~(UJMP | JMP | STORE | LOAD | NOP | STP | PSH | POP)) & Rd[0]);
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assign s4 = EXEC1 & ~(LOAD | STORE);
assign RAMd_wren = EXEC1 & STORE;
assign RAMd_en = EXEC1 & (STORE | LOAD);
assign RAMi_en = EXEC1 & ~STP | EXEC2 & (LOAD | MUL | MLA | MLS);
assign ALU_en = LOAD | STORE;
assign E2 = EXEC1 & (LOAD | MUL | MLA | MLS | POP);
assign stack_en = (EXEC1 & PSH) | POP;
assign stack_rst = STP;
assign stack_rw = POP;
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endmodule