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diff --git a/ISA_notes.md b/ISA_notes.md deleted file mode 100644 index 8f56686..0000000 --- a/ISA_notes.md +++ /dev/null @@ -1,127 +0,0 @@ -# RISC-V full size Instructions Formats (32bit): - -## R-format: op(rs1, rs2) -> rd -`opcode[7] rd[5] funct3[3] rs1[5] rs2[5] funct7[7]` - -register arithmetic/logical -opcode: 0b0110011 / 0x33 - -| funct7 | funct3 | operation | -|========|========|===========| -| 0x0 | 0x0 | ADD | -| 0x20 | 0x0 | SUB | -| 0x0 | 0x1 | SLL | -| 0x0 | 0x2 | SLT | -| 0x0 | 0x3 | SLTU | -| 0x0 | 0x4 | XOR | -| 0x0 | 0x5 | SRL | -| 0x20 | 0x5 | SRA | -| 0x0 | 0x6 | OR | -| 0x0 | 0x7 | AND | - -## I-Format: op(rs1, imm12) -> rd -`opcode[7] rd[5] funct3[3] rs1[5] imm[12]` - -load -opcode: 0b0000011 / 0x03 - -- rs1: base address -- imm12: offset (scaled/signed by funct3) - -| funct3 | operation | | -|========|===========|=====| -| 0x0 | LB | i8 | -| 0x1 | LH | i16 | -| 0x2 | LW | i32 | -| 0x4 | LBU | u8 | -| 0x5 | LHU | u16 | - - -immediate arhitmetic/logical -opcode: 0b0010011 / 0x13 - -- rs1: base address -- imm12: offset (scaled/signed by funct3) - -| funct3 | operation | | -|========|===========|==============================| -| 0x0 | ADDI | | -| 0x2 | SLTI | | -| 0x3 | SLTIU | | -| 0x4 | XORI | | -| 0x6 | ORI | | -| 0x7 | ANDI | | -| 0x1 | SLLI | imm12 = 0b0000000 , shamt[5] | -| 0x5 | SRLI | imm12 = 0b0000000 , shamt[5] | -| 0x5 | SRAI | imm12 = 0b0100000 , shamt[5] | - - -jalr -opcode = 0b1100111 / 0x67 - -- rs1: base address -- imm12: offset (bytes) -- save PC+4 in rd -- jump to offset - -## S-format: op(rs1, rs2, imm12) -`opcode[7] imm4:0[5] funct3[3] rs1[5] rs2[5] imm11:5[7]` - -store -opcode: 0b0100011 / 0x23 - -- rs1: base address -- rs2: data -- imm12: offset (scaled/signed by funct3) - -| funct3 | operation | | -|========|===========|==========================| -| 0x0 | SB | i8, imm12 in bytes | -| 0x1 | SH | i16, imm12 in half-words | -| 0x2 | SW | i32, imm13 in words | - -## B-format: op(rs1, rs2, imm12/13) -`opcode[7] imm11[1] imm4:1[4] funct3[3] rs1[5] rs2[5] imm10:5[6] imm12[1]` - -branch -opcode = 0b1100011 / 0x63 - -- rs1, rs2: registers to compare -- imm12/13: PC offset in half-words - -| funct3 | operation | -|========|===========| -| 0x0 | BEQ | -| 0x1 | BNE | -| 0x4 | BLT | -| 0x5 | BGE | -| 0x6 | BLTU | -| 0x7 | BGEU | - -## U-Format: op(imm20/32) -> rd -`opcode[7] rd[5] imm31:12[20]` -upper-bit immediates (lui, auipc) - -lui -opcode: 0b0110111 / 0x37 - -- imm20: top 20 bits of rd -- clears bottom 12 bits -- combine lui + addi to load 32bit immediate - NOTE: sign extension requires some trickery. - -auipc: -opcode: 0b0010111 / 0x17 - -- imm20: top 20 bits of offset added to PC -- result stored in rd - -## J-Format: op(imm20/21) -> rd -`opcode[7] rd[5] imm31:12[20]` -immediates on a 32bit scale (jal) - -jal -opcode = 0b1101111 / 0x6f - -- save PC+4 in rd -- imm20/21: PC offset in half-words |