[PDF] 6502 undocumented opcodes

  • How many Opcodes does the 6502 have?

    Of the 256 possible opcodes available using an 8-bit pattern, the original 6502 uses 151 of them, organized into 56 instructions with (possibly) multiple addressing modes. Depending on the instruction and addressing mode, the opcode may require zero, one or two additional bytes for operands.

  • How many Opcodes does the NES have?

    The opcode is a byte value in the range 0 to 255 inclusive. The 6502 supports 151 opcodes and they are grouped into 56 operations. Each opcode in a group performs the same basic operation, such as adding two numbers together. They differ by the addressing mode used to specify the data to operate on.

  • What is the 6502 ADC instruction?

    The 6502 has an 8-bit addition operation ADC (add with carry) which adds two numbers and a carry-in bit, yielding an 8-bit result and a carry out bit. The following diagram shows an example addition in binary, decimal, and hexadecimal.
  • ROL (ROtate Left)
    ROL shifts all bits left one position. The Carry is shifted into bit 0 and the original bit 7 is shifted into the Carry.
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The C74-6502 implements all NMOS 6502 and WDC 65C02 instructions interrupts and functions



atasm.pdf

undocumented 6502 instructions listed in Appendix C. Without this flag the undocumented opcodes will generate assembly errors. Notice that due to their.



NMOS 6510 Unintended Opcodes

'Back in the days' so called 'illegal' opcodes were researched independently by opcodes are known to work slightly different on 6502 equipped machines.



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Illegal Opcodes. 8. Opcode format. 9. Reverse Engineering the MOS 6502 CPU. 10. Beregnyei Balazs' full transistor-level schematic. 11. An. Interview.



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'Back in the days' so called 'illegal' opcodes were researched independently by The instructions of the 6502 are compressed into a 130-entry decode ROM.



Diploma thesis

16.07.2012 circuit chosen for the simulation is a complete MOS 6502 CPU which was ... of the IR to an undocumented opcode that is known to deadlock.



Altirra Hardware Reference Manual - VirtualDub

07.07.2022 CPU: Fixed some erroneous illegal instructions in the 6502 opcode chart. ... new 65C816 functionality undocumented 6502 opcodes



Implementing the Nintendo Entertainment System on a FPGA

25.06.2013 Nintendo used the MOS 6502 processor that itself was once an ... some undocumented opcodes)



vasm assembler system

Many common directives/pseudo-opcodes are supported (depending on the syntax module) -illegal Allow 'illegal' 6502 instructions to be recognized.



6502 Instruction Set

6502 Instruction Set. TOC: Description / Instructions in Detail / "Illegal" Opcodes / Jump Vectors and Stack Operations / Instruction Layout / 65xx-Family.

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