77 lines
2.6 KiB
Plaintext
77 lines
2.6 KiB
Plaintext
instructions needed (R, I, S, B)
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ops needed:
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NOP (I) opcode: 001 0011, funct3: 000 note: same encoding as addi x0, x0, 0
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ADD (R) opcode: 011 0011, funct3: 000, funct7: 000 0000
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SUB (R) opcode: 011 0011, funct3: 000, funct7: 010 0000
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SLL (R) opcode: 011 0011, funct3: 001, funct7: 000 0000
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SRL (R) opcode: 011 0011, funct3: 101, funct7: 000 0000
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ADDI (I) opcode: 001 0011, funct3: 000
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LOAD (I) opcode: 000 0011, funct3: 010
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STORE (S) opcode: 010 0011, funct3: 010
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BEQ (B) opcode: 110 0011, funct3: 000
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EBREAK (I) opcode: 111 0011, funct3: 000
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- opcode [6:0]
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- funct3 [14:12]
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- rs1 [19:15]
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R type
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- opcode: 011 0011
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- funct7 [31:25]
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- rs2 [24:20]
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- rs1 [19:15]
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- funct3 [14:12]
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- rd [11:7]
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- opcode [6:0]
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I type
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- opcode: 001 0011 | 000 0011
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- imm [31:20]
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- rs1 [19:15]
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- funct3 [14:12]
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- rd [11:7]
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- opcode [6:0]
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S type
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- opcode: 010 0011
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- imm [31:25]
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- rs2 [24:20]
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- rs1 [19:15]
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- funct3 [14:12]
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- imm [11:7]
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- opcode [6:0]
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B type
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- opcode: 110 0011
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- imm [31:25]
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- rs2 [24:20]
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- rs1 [19:15]
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- funct3 [14:12]
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- imm [11:7]
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- opcode [6:0]
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main decoder truth table
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instr opcode regwrite immsrc alusrc memwrite resultsrc branch aluop
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add 0110011 1 xx 0 0 0 0 10
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sub 0110011 1 xx 0 0 0 0 10
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sll 0110011 1 xx 0 0 0 0 10
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srl 0110011 1 xx 0 0 0 0 10
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addi 0010011 1 00 1 0 0 0 10
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lw 0000011 1 00 1 0 1 0 00
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sw 0100011 0 01 1 1 x 0 00
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beq 1100011 0 10 0 0 x 1 01
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ebreak 1110011 x xx 0 0 0 1 01
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alu decoder truth table
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aluop funct3 {op[5], funct7[5]} alucontrol instruction
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00 x x 00 (add) lw, sw
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01 x x 01 (sub) beq
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10 000 00, 01, 10 00 (add) add, addi
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000 11 01 (sub) sub
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001 x 10 (sll) sll
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101 x 11 (srl) srl
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