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Specification.md

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Processor Specification

The PATP is an 8-bit microprocessor with a 5-bit address space. The processor features:

  • A whopping 32 bytes of memory
  • A 5 bit program counter
  • A single accumulator register
  • A CCR with only one bit flag (set when the result of an operation is zero)

Assembly language

  • Each instruction is 8 bits: 3 for the opcode and 5 for the operand.
  • Operands should be specified as denary numbers
Opcode Operand Description
CLEAR None Set accumulator to 0 (and set Z flag).
INC None Increment accumulator. Z is set if the result is 0.
DEC None Decrement accumulator. Z is set if the result is 0.
ADD Integer Add the operand to the accumulator, storing the result back in the accumulator. Z is set if the result is 0.
LOAD Memory location Load the value from the location given into the accumulator.
STORE Memory location Store the value in the accumulator at the memory location given.
JMP Memory location Jump to the instruction at the memory location given
BNZ Memory location Branch to the instruction at the memory location given if the previous instruction set Z to 0.
STOP None Halts execution.

Programs are loaded into memory at 0, and instructions and data share memory. If you write a program larger than 32 bytes, the emulator won't load it.