4917 Microprocessor Emulator

Architecture

There are 16 Memory locations and 4 registers
Each memory location and register holds a number between 0 and 15
all arithmetic operations are mod 16.

• IP = Instruction Pointer
• IS = Instruction Store
• R0 = General Register 0
• R1 = General Register 1

Instruction Codes

• 1-byte1 Instructions
• 0 = Halt
• 1 = Add (R0 = R0 + R1)
• 2 = Subtract (R0 = R0 - R1)
• 3 = Increment R0 (R0 = R0 + 1)
• 4 = Increment R1 (R1 = R1 + 1)
• 5 = Decrement R0 (R0 = R0 - 1)
• 6 = Decrement R1 (R1 = R1 - 1)
• 7 = Ring Bell
• 2-byte Instructions, value of the second byte is called [data]
• 8 = Print [data] (The numerical value of [data] is printed)
• 9 = Load value at address [data] into R0
• 10 = Load value at address [data] into R1
• 11 = Store R0 into address [data]
• 12 = Store R1 into address [data]
• 13 = Jump to address [data]
• 14 = Jump to address [data] if R0 == 0
• 15 = Jump to address [data] if R0 != 0