So, basically, I have an exam on Wednesday, and I started studying the 68k assembly on Friday, because I've been busy studying for the math exam, passed on Friday (I know you don't care, but I say this so you don't think I'm an a******.) Anyway, I'm trying to write a subroutine, that compares the [i] with the numer #12. IF [i]=#12, then memory offset ($8200+[i])=D3-#1, ELSE memory offset($8100+[i])=2*D3. When I try to assemble this (using ASIMTOOL), it gives me these errors
ERROR in line 10: Displacement out of range
ERROR in line 12: Displacement out of range
ERROR in line 15: Invalid syntax
ERROR in line 16: Invalid syntax
I know this code it's a load of s*it, but I've no one assisting me and I'm trying to do this by myself. If you could help, it would awesome, thank you. Here's the code:
ORG $8000
START MOVE.l #0,D3
MOVEA.l #$8200,a0
MOVEA.l #$8100,a1
CMP.w #12,i
BEQ.s VERO
JMP FALSO
VERO: SUB.w #1,D3
MOVE.l D3,i(a0)
FALSO: MULU.w #2,D3
MOVE.w D3,i(a1)
STOP #2000
i DC.w 12
x DC.w #4
y DC.w #3
END START
You might want to download the M68000 Programmer's Reference Manual. Here's a summary of the addressing modes from that document ("Table 2-4. Effective Addressing Modes and Categories"):
Addressing Modes Syntax
Register Direct
Data Dn
Address An
Register Indirect
Address (An)
Address with Postincrement (An)+
Address with Predecrement -(An)
Address with Displacement (d16,An)
Address Register Indirect with Index
8-Bit Displacement (d8,An,Xn)
Base Displacement (bd,An,Xn)
Memory Indirect
Postindexed ([bd,An],Xn,od)
Preindexed ([bd,An,Xn],od)
Program Counter Indirect
with Displacement (d16,PC)
Program Counter Indirect with Index
8-Bit Displacement (d8,PC,Xn)
Base Displacement (bd,PC,Xn)
Program Counter Memory Indirect
Postindexed ([bd,PC],Xn,od)
Preindexed ([bd,PC,Xn],od)
Absolute Data Addressing
Short (xxx).W
Long (xxx).L
Immediate #<xxx>
The addressing mode matching MOVE.l D3,i(a0) is "Register Indirect, Address with Displacement". The problem is that you seem to be trying to load the value from a variable and use it as a displacement in a single instruction. The displacement needs to be an immediate constant, so that's why it's not working. What you could do instead is use ADDA to add the value of i to a0 and then do move.l d3,(a0).
And you should probably remove the # signs from your DC.ws.