The A-instruction: symbolic and binary syntax Semantics: Set the A register to value Symbolic syntax: @value Where value is either: a non-negative decimal constant ≤32767 (=215-1) or a symbol referring to such a constant (later) Example: @21 Effect: sets the A register to 21 Binary syntax: Ovvvvvvvvvvvvvvvv For example: @21 (symbolic syntax- assembly code) 0000000000010101 (binary syntax- machine code) Symbolic syntax: dest = comp; jump Binary syntax: 1 1 1 a c1 c2 c3 c4 c5 c6 d1 d2 d3 j1 j2 j3 dest d1 d2 d3 effect: the value is stored in: The value is not stored 1 RAM[A] 10D register 0 1 1 RAM[A] and D register A register 101 1 1 0 comp c1 c2 c3 c4 c5 c6 0 101 010 null 1 -1 1 1 1 1 1 1 1 1 1 0 1 0 M D D 0 0 1 1 0 0 MD A M 1 1 0 0 0 0 A 1 ID 0 0 110 1 AM IA IA IM 1 1 0 0 0 1 AD 0 -D 001111 AMD 1 1 1 A -A -M D+1 A+1 M+1 D-1 1 1 0 0 1 1 01 1 1 1 1 1 10 11 1 001110 jump null A-1 M-1 110010 JGT JEQ D+A D+M D-A D-M 010011 JGE 0 1 1 A-D M-D JLT 100 D&A D&M ONE DIA D❘M 0 1 0 1 0 1 JLE a-0 a-1 JMP j1 j2 j3 A register and RAM[A] A register and D register A register, RAM[A], and D register effect: eno jump 001 if out > jump 0 1 0 if out 0 jump if out 20 jump if out < jump 101 if out 0 jump 110 if out se jump 1 1 1 Unconditional jump Recall the two Assembly Instructions, A and C: The A-instruction Syntax: @value The C-instruction Where value is either: a a non-negative decimal constant or dest comp; jump (both dest and jump are optional) where: aa symbol referring to such a constant (later) comp= Semantics: dest=null, M, D, MD, A, AM, AD, AMD ⚫Sets the A register to value ⚫Side effect: RAM[A] becomes the selected RAM register Example: @21 Effect: Sets the A register to 21 RAM[21] becomes the selected RAM register e, 1, -1, D, A, ID, IA, D, -A, D+1, A+1, D-1, A-1, D+A, D-A, A-D, D&A, DIA M, IM, -M, M+1, M-1, D+M, D-M, M-D, D&M, DIM. M refers to RAM[A] jump null, GT, JEQ, JGE, LT, JNE, JLE, JMP Semantics: Compute the value of comp Stores the result in dest; If the Boolean expression (comp jump 0) is true, jumps to execute the instruction stored in ROM[A]. if (comp jump 0) jump to execute the instruction in ROM[A] + parts values parts values A=D&M D=A parts D=M values parts values D=D|A parts D=!D www values parts M=A values M=D parts values