IA6805E2
29 August 2007
Microprocessor Unit
As of Production Version 00
Instruction Set Description
The MPU has 61 basic instructions divided into 5 types. The 5 types are Register/memory, read-
modify-write, branch, bit manipulation, and control.
Register/Memory Instructions:
Most of the following instructions use two operands. One is either the accumulator or the
index register and the other is obtained from memory. The jump unconditional (JMP) and
jump to subroutine (JSR) instructions have no register operand.
Function
Load A from memory
Load X from memory
M nemonic
LDA
LDX
STA
Store A in memory
Store X in memory
STX
Add memory to A
Add memory and carry to A
Subtract memory
ADD
ADC
SUB
Subtract memory from A with Borrow
AND memory to A
OR memory with A
Exclusive OR memory with A
Arithmetic compare A with memory
Arithmetic compare X with memory
Bit test memory with A (logical compare)
Jump Unconditional
SBC
AND
ORA
EOR
CMP
CPX
BIT
JMP
Jump to subroutine
JSR
Read-Modify-Write Instructions:
These instructions read a memory or register location, modify or test its contents and then
write the modified value back to memory or the register.
Function
Increment
Mnemonic
INC
Decrement
Clear
DEC
CLR
Complement
COM
NEG
ROL
ROR
LSL
Negate (2's complement)
Rotate Left Thru Carry
Rotate Right Thru Carry
Logical shift left
Logical shift right
Arithmetic shift right
Test for negative or zero
LSR
ASR
TST
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