Motorola HC12 Manuale Utente
User’s Manual
MCUez HC12 Assembler
132
Assembler Syntax
MOTOROLA
Assembler Syntax
7.4.3.4 Extended
The extended addressing mode is used to access memory located above the
direct page in a 64-Kbyte memory map.
direct page in a 64-Kbyte memory map.
Example:
XDEF Entry
ORG $100
data: DS.B 1
MyCode: SECTION
Entry:
LDS #$AFE
; init Stack Pointer
LDAA #$01
main: STAA data
BRA main
In this example, the value in register A is stored in the variable
data
. This
variable is located at address $0100 in the memory map.
7.4.3.5 Relative
This addressing mode is used to determine the destination address of branch
instructions. Each conditional branch instruction tests some bits in the condition
code register. If the bits are in the expected state, the specified offset is added
to the address of the instruction following the branch instruction, and execution
continues at that address.
instructions. Each conditional branch instruction tests some bits in the condition
code register. If the bits are in the expected state, the specified offset is added
to the address of the instruction following the branch instruction, and execution
continues at that address.
Short branch instructions (BRA, BEQ, etc.) expect a signed offset encoded on
one byte. The valid range for a short branch offset is [–128...127].
one byte. The valid range for a short branch offset is [–128...127].
Example:
main:
NOP
NOP
BRA main
In this example, after the two
NOP
s have been executed, the application
branches on the first
NOP
and continues execution.