6809/6309 Mnemonic Lookup

You can lookup a single instruction by typing LD in the instruction field, which will show all load instructions. You can also lookup multiple instructions like LD,CMP.

You can also lookup mnemonics like LDX,LDY in the mnemonic field.

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Instruction: Lookup

Mnemonic: Lookup

* = 6309		Immediate			Direct			Indexed			Extended			Inherent			Relative			Register			Memory
*	Mnemonic	Opcode	Cycles	Length	Opcode	Cycles	Length	Opcode	Cycles	Length	Opcode	Cycles	Length	Opcode	Cycles	Length	Opcode	Cycles	Length	Opcode	Cycles	Length	Opcode	Cycles	Length
*	CMPE	1181	3	3	1191	5/4	3	11A1	5+	3+	11B1	6/5	4

Description:

Compare Memory Byte from 8-Bit Accumulator [TEMP <- r - (M)]

Documenation

These instructions subtract the contents of a byte in memory from the value contained in one of the 8-bit accumulators (A,B,E,F) and set the Condition Codes accordingly. Neither the memory byte nor the accumulator are modied.

• H - The affect on the Half-Carry ag is undefined for these instructions.
• N - The Negative flag is set equal to the value of bit 7 of the result.
• Z - The Zero flag is set if the resulting value is zero; cleared otherwise.
• V - The Overow flag is set if an overflow occurred; cleared otherwise.
• C - The Carry flag is set if a borrow into bit-7 was needed; cleared otherwise.

The Compare instructions are usually used to set the Condition Code flags prior to executing a conditional branch instruction.

The 8-bit CMP instructions perform exactly the same operation as the 8-bit SUB instructions, with the exception that the value in the accumulator is not changed. Note that since a subtraction is performed, the Carry ag actually represents a Borrow.

Example

 lda #3
 cmpa #3   *check if reg A is 3, immediate mode
 beq three *yup, A is 3
 *falls through if A is not 3