MARIE

• MARIE - Machine Architecture that is Really Intuitive and Easy
• Designed by our authors
  • 4096 addresses
  • 16 bit word,
  • word addressable
  • MMU as described before
  • 1 register - called an accumulator
  • PC -starts at 0, as described before
  • ALU
  • CU - control unit.
  • IR - instruction register - stores the current instruction
  • A common bus, 16 bits wide
• Instruction Set Architecture (ISA)
  • 16 bit instruction
    • 4 bit opcode (bits 12-15)
    • 12 bit operand (bits 0 - 11)
    • With 4 bits we can have 2⁴ or 16 instructions
  • Register Transfer Notation
    • Memory is an treated as an array M[4] is memory location 4
    • <- is a transfer operation, data flows from the left to right
    • Registers (PC, IR, ACC, MBR, MAR) or units (ALU)
    • MAR <- PC (load the mar from the pc)
    • This involves a bus transfer which we will ignore for now.
  • Load
    • Load a value from memory into the acc
    • OP Code = 0001 (1₁₆)
    • Operand address to load
    • MAR <- IR_0-11
    • MBR <- M[MAR]
    • ACC <- MBR
  • Store
    • Save the value of the acc to memory
    • Op Code = 0010 (2₁₆)
    • Operand address to store at
    • MAR <- IR_0-11
    • ACC <- MBR
    • M[MAR] <- MBR
  • Add
    • OP Code = 0011 (3₁₆)
    • Operand address of value to add to acc
    • MAR <- IR_0-11
    • MBR <- M[MAR]
    • ACC <- ACC + MBR
  • Sub
    • OP Code = 0100 (4₁₆)
    • Operand address of value to subtract from acc
    • MAR <- IR_0-11
    • MBR <- M[MAR]
    • ACC <- ACC - MBR
  • Input (0101, ACC <-InReg)
  • Output (0110, OutReg<-ACC);
  • Halt (0111, Stop Execution)
  • SkipCond
    • Op Code = 1000
    • IR_10-11 = Condition

    • if (Condition ==0) {
           if (ACC < 0) {
              PC<- PC + 1
           }
      } else if (condition == 01) {
           if (ACC == 0) {
              PC<- PC + 1
           }
      } else if (condition == 10) {
           if (ACC > 0) {
              PC<- PC + 1
           }
      }
      	    

  • Jump
    • Opcode 1001
    • IR_0-11 the address we wish to jump to
    • PC <- IR_0-11
  • Clear
    • Opcode 1010
    • ACC <- 0
• Assume that two numbers are stored at 100 and 101. Compute their sum and store it at 102.
• Assume that three numbers are stored at 100, 101, and 102. store the largest in the acc.
• There is a simulator for marie available Here
• There is my partial tk-gate implementation of marie available as well.