ORG 0x05C6
START: CLA
ST result
LD X
INC
PUSH
CALL 0x06E5
POP
ADD result
ST result
LD Z
PUSH
CALL 0x06E5
POP
ADD result
ST result
LD Y
DEC
PUSH
CALL 0x06E5
POP
SUB result
ST result
HLT
Z: WORD 0xFFF4
Y: WORD 0x0000
X: WORD 0xFDDE
result: WORD ?

ORG 0x06E5
LD &1
BEQ A
BPL B
A: CMP const1
BLT B
BEQ B
ASL 
ASL
SUB &1
ADD const2
JUMP C
B: LD const1
C: ST &1
RET
const1: WORD 0xFAB3
const2: WORD 0x0064