MICRO-CONTROLLER MOTOROLA HCS12Addressing Modes

Mechatronics

Department

Faculty of EngineeringAin Shams Univeristy

HCS12 Addressing Modes

HCS12 instruction set can be categorized according to the type of operand used for every instruction.

Immediate Addressing. Direct/Extended Addressing. Indexed Addressing. Inherent Addressing. Relative Addressing.

HCS12 Programmer’s model Accumulator (Operand Register). Index Registers X&Y (Keeps

addresses for specific instructions using addresses as operands).

Stack Pointer (Keeps track of program stack in the Ram).

Program Counter (Keeps track of the program script).

A B

X

Y

SP

PC

$ 5000

$ 5001 Op-Code

$ 5002 Operand

$ 5003

$ 5004

$ 5005

Instruction Set Example

ldaa#$64; ldaa#$6464; Operand

Immediate Addressing ldaa#$64;

# = Immediate

A B

X

Y

SP

PC

#$64

Direct Addressing ldaa$64;

No sign= Direct Addressing

A B

X

Y

SP

PC

$ 0063 ……

$ 0064 $FF

$ 0065 ……

$64

$FF

Extended Addressing ldd $1234;

2 bytes operand= Extended Addressing

D

X

Y

SP

PC

$ 1233 ……

$ 1234 $FF

$ 1235 $FF

$1234

$FF$FF

Indexed Addressing ldaa!1,x;

Use index register X, Y, SP or PC

A B

X $0064

Y

SP

PC

$ 0064 ……

$ 0065 $FF

$ 0066 ……

$0064

$FF

+1

$0065

Indexed Pre-decrement Addressing

ldaa!1,-x;

Use sign before index register X, Y, SP or PC

A B

X $0065

Y

SP

PC

$ 0064 $FF

$ 0065 ……

$ 0066 ……

$0064

$FF

-1

$0065$0064

Indexed Post-increment Addressing

ldaa!1,x+;

Use sign after index register X, Y, SP or PC

A B

X $0064

Y

SP

PC

$ 0064 $FF

$ 0065 ……

$ 0066 ……

$0064

$FF

+1

$0065$0064

Indexed Indirect Addressing ldaa[!1,x];

Use [ ] with index register X, Y, SP or PC

A B

X $0064

Y

SP

PC

$ 0064 ……

$ 0065 $00

$ 0066 $67

$ 0067 $FF

$0064

$FF

+1

$0065 $006

7$0067

Eng. Mohamed Mahmoud Hamdy

Eng. Mostafa Ahmed Arafa

Prepared by: