FINISHED SIA REPOSITORY (from desktop)

Takes text files with valid language as input and uses it to create assembly. The assembly file can then be used to run instructions.

Input a text file with lines similar to those found in the SIA/cAssemblerInput file, into the SIA/Assembler.c execution (via command line or ide) Take output binary file from sia (cAssemblerOutput) and input into SIAVM/siavm.c.

(Does not include pipeline addition of other SIA repository, just linear sequence)

SPECS by M Phipps

Written by Philip R Smith Nov 2019

• add (opcode 1) Adds the values of 2 registers and places the answer in a third register. Example: add r1 r2 r3 ; r3  r1 + r2 Instruction format: 3R

• addimmediate (opcode 9) Adds a signed 8 bit value to a register Example: addimediate r1 -127 ; adds -127 to r1 Instruction format: ai

• and (opcode 2) Preforms a bitwise and on 2 registers and stores the result in a third register Example: and r1 r2 r3 ; r3  r1 & r2 Instruction format: 3R

• branchifequal (opcode 10) Compares two registers – if they hold the same value, jump to an offset from the current program counter. The offset can be between -524,286 and 524,286. The offset is the number of words (2 bytes) forward or back. PC <= PC + (2 * offset). Example: branchifequal r1 r2 1000
  Instruction format: br

• branchIfless (opcode 11) Compares two registers – if the first is less than the second, jump to an offset from the current program counter. The offset can be between -524,286 and 524,286. The offset is the number of words (2 bytes) forward or back. PC <= PC + (2 * offset). Example: branchifless r1 r2 1000 Instruction format: br

• call (opcode 13) Calls a “function” – pushes the PC of the next instruction onto the stack (R15), then jumps to the address specified by this instruction times 2 (0 – 1,073,741,824). Example: call 444 Instruction format: jmp

• divide (opcode 3) Divides the value of the first register by the second and places the answer in a third register. This is integer math with the fractional portion discarded. Example: divide r1 r2 r3 ; r3  r1 / r2 Instruction format: 3R

• halt (opcode 0) Stops the CPU. Example: halt Instruction format: 3R (the register values don’t matter)

• interrupt (opcode 8) Interrupts the CPU using a particular interrupt number. This could be used to jump between kernel mode and user mode or to support devices. For the virtual machine, two interrupts are supported: 0 (print registers) and 1 (print out memory) Example: interrupt 17 Instruction format: int

• jump (opcode 12) Jumps to the location specified in the instruction times 2 (0 – 1,073,741,824) Example: jump 1000 instruction format: jmp load (opcode 14) Loads a register from the memory pointed to by another register plus 2 times the offset (0 to 30). Note that both the address in the register and the offset are in words (memory locations). Example: load r1 r2 10 ; loads r1 with the value pointed to by r2 plus 20 bytes instruction format: ls

• multiply (opcode 4) Multiplies the value of the first register times the second and places the answer in a third register. Example: multiply r1 r2 r3 ; r3  r1 * r2 Instruction format: 3R

• or (opcode 6) Performs a bitwise OR on 2 registers and stores the result in a third register Example: or r1 r2 r3 ; r3  r1 | r2 Instruction format: 3R

• pop (opcode 7) Copies data from stack pointer through stack pointer + 3 to specified register. Adds four to the stack pointer. Example: pop R1 Instruction format: stack

• push (opcode 7) Subtracts four from the stack pointer. Takes the value in the specified register and stores it in the memory address indicated by the stack pointer. Example: pop R1 Instruction format: stack

• return (opcode 7) Pops the top value from the stack and jumps to that address Example: return Instruction format: stack

• store (opcode 15) Stores a register’s value into memory memory pointed to by another register plus 2 times the offset (0 to 30). Note that both the address in the register and the offset are in words (memory locations). Example: store r1 r2 10 ; stores r1’s value into the memory pointed to by r2 plus 20 bytes instruction format: ls

• subtract (opcode 5) Subtracts the value of the second register from the first and places the answer in a third register. Example: subtract r1 r2 r3 ; r3  r1 - r2 Instruction format: 3R