Chapter 27. M68HC11 and M68HC12 Dependent Features

161

Address Register

number,X

,

number,Y

The

number

may be omitted in which case 0 is assumed.

Direct Addressing mode

*symbol

, or

*digits

Absolute

symbol

, or

digits

The M68HC12 has other more complex addressing modes. All of them are supported and they are

represented below:

Constant Offset Indexed Addressing Mode

number,reg

The

number

may be omitted in which case 0 is assumed. The register can be either

X

,

Y

,

SP

or

PC

. The assembler will use the smaller post byte definition according to the constant value (5 bit

constant offset, 9 bit constant offset or 16 bit constant offset). If the constant is not known by the

assembler it will use the 16 bit constant offset post byte and the value will be resolved at link

time.

Offset Indexed Indirect

[number,reg]

The register can be either

X

,

Y

,

SP

or

PC

.

Auto Pre Increment/Pre Decrement/Post Increment/Post Decrement

number, reg number,+reg number,reg  number,reg+

The number must be in the range

 8

..

+8

and must not be 0. The register can be either

X

,

Y

,

SP

or

PC

.

Accumulator Offset

acc,reg

The accumulator register can be either

A

,

B

or

D

. The register can be either

X

,

Y

,

SP

or

PC

.

Accumulator D offset indexed indirect

[D,reg]

The register can be either

X

,

Y

,

SP

or

PC

.

For example:

ldab 1024,sp

ldd [10,x]

orab 3,+x

stab  2,y 

ldx a,pc

sty [d,sp]