6805 Instructions 

Condition Code Register

Read/Write/Modify Instructions  - 6805 book pp. 122 -instructions that read a memory location or register, modify its contents and write the modified value back to a memory location or register.

• shifts and rotates:  LSL, LSR, ASR, ROR, ROL
• bit sets and clears: BSET, BCLR
• clear register: CLR
• increment, decrement: INC, DEC
• complements: COM  NEG

Jump and Branch instructions - 6805 book pp. 123 instructions that can interrupt the normal sequence of incrementing PC.

• Branch always and never: BRA, BRN
• Unconditional jump: JMP
• Branch if flag is true: BCS, BEQ, BHCS, BMI,
• Branch if flag is false: BCC, BNE, BHCC, BPL
• Branch to Subroutine: BSR
• Jump to Subroutine: JSR
• Branch if Bit Set or Clear: BRSET, BRSET

Control Instructions - 6805 book pp. 124

• Set or clear flags: SEC, SEI, CLC, CLI
• No operation: NOP
• Return from subroutine: RTS
• Return from interrupt: RTI
• Transfer A and X: TAX, TXA

Example Programs