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JMP
Jump to New Location

Addressing mode   Mnemonic     Opcode    Length     Exec.Time
Absolute          JMP $xxxx    4C        3          3
Indirect          JMP ($xxxx)  6C        3          5

Doesn't affect status register.

JMP will simply jump to the specified memory location.

NOTE: See 6502 indirect JMP bug for a warning about the indirect mode. (Basically says what yerricde says below...)

(Back to 6502 Opcodes Metanode)

(Source: Eskoensio Pipatti: Basicista Konekieleen: Konekieliopas 6502-prosessorille, MikroBITTI-kirjat Technopress OY, 1989, ISBN 951-832-006-3; Also Verified from couple of web pages just to make sure. So there. =)

A 6502 instruction that jumps to (sets the program counter to point at) an instruction stream at a given address.
  • Function: &N => PC
  • Updates flags: none
  • Opcode numbers:
    abs   $4C (3 bytes, 3 cycles)
    (a)   $6C (3 bytes, 5 cycles)
    

Warning about indirect JMP

Because there is no carry associated with retrieving the most significant byte of the address that a JMP (a) points to, the (a) form should NEVER have a low-order byte of $FF. For example,

  jmp ($89ff)
will fetch the program counter from $89ff and $8900, instead of $89ff and $8a00 as expected. All other 6502 indirect addressing modes have the same "feature."

Similar: JSR
See also: 6502 instructions | 6502 addressing modes

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