Pl EXOS 1.DOC
EXERCISES I
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- Solutions to the exercises proposed in this file are present
in the file: CORRIG_1.DOC
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You just need to note the exercise number whose answer you want to know.
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No. 1:
Find the error (easy...)
text
ab move.b #345,d0
add.b #1,d0
jmp ab
end
No. 2:
What will the data register d3 contain?
text
move.l #12,d3
add.l #4,d3
add.l d3,d3
move.l var,d2
add.l d2,d3
data ;data segment
var dc.l 458
end
No. 3:
What will the d5 register contain?
text
move ici,d4
add #5,d4
move d4,la
add ici,la
move la,d5
data
ici dc.w 10
bss
la ds.w 1
end
No. 4:
Find the value of a4 at the end of the program knowing that the label 'ad' is located at an address equal to $ff0 and it points to (dc.l) the number 45
Find the value of d5:
text
move.l #ad,a4
move.l ad,d5
data
ad dc.l 45 ; it is assumed that here PC=$ff0
end
No. 5:
Find the value of d5 and a5 following this program.
text
move #15,d5
move.l #zz,a5
move.w zz,d5
data
zz dc.w 0
end
- I will now use the control operation instruction 'DBF' which allows the
execution of a loop and whose syntax is: 'DBF Dn,loop'. This instruction uses a data register Dn and a Destination Label. Each call, Dn is decremented by 1 unit, if Dn equals -1, the program continues after the instruction that follows 'DBF' otherwise the instruction performs a jump to the Destination address.
example:
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text
move.b #1,d3 ;d3=1 from the beginning
move.w #99,d0 ;number of loops -1 (because we go until -1!)
tgv add.b #1,d3 ;we add 1 to d3 until d0=-1, so
dbf d0,tgv ;100 times in a row
move.b d3,var ;then we put d3.b (=101) in var
;NB: d0 equals -1 ...
bss
var ds.b 1
end
No. 6:
Find the value contained at the address out, the value of d0 and d5 at the end of this program.
text
move #247,d0
move #3,d5
bbb add #8,d0
move d0,out
dbf d5,bbb
bss
out ds.b 2
end
No. 7:
Find the BINARY value of the data register d1 at the end of this program. NB:5438=%0001010100111110
text
move #5391,d0
add #47,d0
move d0,dix
move.b in,d1
bss
dix ds.b 1 in ds.w 47
data
nul dc.w 5438
end
No. 8:
what will happen at 'gag'?
text
move.l #gag,a2
gag move.b #100,d1
jmp (a2)
end
No. 9:
What will be the value of d3 after this program?
text
move.b #12,lab
move.b #14,lac
move.b #15,lad
move.l #lab,a3
move.b #1,d1
fff move.b (a3)+,d3
dbf d1,fff
add.b (a3),-(a3)
move.b -(a3),d3
add.b (a3),d3
bss
lab ds.w 1 lac ds.b 1 lad ds.w 5
end
No. 10:
What will be the values of d0,d1,d2,d3,a0 after this program?
text
move.b #10,a
move.b #11,b
move.b #12,c
move.b #13,d
move.b #98,e
move.l #deb,a0
move.b (a0)+,d0
move.b (a0)+,d1
move.b (a0)+,d2
move.b (a0),d3
move.b -(a0),d4
bss
deb ds.b 1 a ds.b 1 b ds.b 1 c ds.b 1 d ds.b 1 e ds.b 1 f ds.l 4
end
No. 11:
Find the value of a4 and d0,d1 after this program.
text
move.b #3,d0
move.l #pil,a4
rrr move.b -(a4),d1
add.b #4,d1
dbf d0,rrr
data
dc.b 1,2,3,4,5,6,7,8,9
pil dc.w 245
end
No. 12:
Find out what is in 'out' and the value of d2.
text
a equ 3 b equ 5
move.b a,d2
add.b b,d2
move.l #g,a5
move.b d2,(a5)
move.b d2,-(a5)
move.b (a5)+,d2
move.b (a5),d2
bss
out ds.b 1 g ds.b 4
end
No. 13:
Find the value of d1,d2,d3,d4 and a0.
text
move.l #out,a0
move.w #2,d3
move.w (a0),d1
move.w -4(a0),d2
move.w -4(a0,d3),d3
move.w -(a0),d4
data
dc.l 1
dc.w 12
dc.w 2356
out dc.b 15
end
No. 14:
What are the different values taken by a0 during this program? What is the final value contained in 'res'?
text
move.l #a,a5
move.l #2,d2
ttt move.b #1,(a5)+
dbf d2,ttt
move.b #5,(a5)
move.l #vec,a1
move.b #3,d0
move.b #0,d2
cde move.l 0(a1,d2),a0
add.l #4,d2
move.b (a0),res
dbf d0,cde
data
vec dc.l a,b,c,d
bss
a ds.b 1 b ds.b 1 c ds.b 1 d ds.b 1 res ds.b 1
end
No. 15:
Find the value pointed by ret, at the end of this program.
text
move.l #5,a
move.l #a,a0
move.l (a0)+,d2
move.l d2,ret
bss
a ds.l 2 ret ds.l 1
end
No. 16:
Find the value of d0 and a0 after this program.
text
move.b #3,d1
move.b #a,a0
mno move.b 1(a0,d1),d0
add.b #14,d0
add.b a,d0
dbf d1,mno
data
a dc.b 0,5,6,7,8,9
end
No. 17:
Find the value of d3 after this program.
text
move.l #a,a0
move.b #5,(a0)+
move.b #6,(a0)+
move.b -(a0),d2
move.l #a,a0
move.b 1(a0),d3
add.b d2,d3
bss
a ds.w 1
ds.b 1
end
No. 18:
Find out what happens at 'stp', what does 'res' contain?
text
move.w #5,d3
add.b #6,d2
add.b d2,d3
move.l #ad,a0
stp jmp 10(a0)
ad move.l #5,res
move.b d3,res
bss
res ds.b 1
end
No. 19:
Now some quick questions:
a) If I write 'MOVE.W #0,d0', what will happen at the level of the CCR?
And if I write afterwards 'ADD.W #-2,d0'?
b) Can we place a BYTE at an odd address?
c) How many digits is an L-M encoded in HEXADECIMAL?
d) Can we use the PC to store a digit as with a data or address register?
(I remind you that it is a register). If yes, how?
e) The directive 'END' ends the program and allows the return to the DESKTOP,
True or False? Argue.
f) A macro instruction is a subroutine called by the Linker every
time it encounters its name in the object code. True or False? Explain.
g) You can use any addressing mode for the operands of the
68000 instructions. True or False?
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When you are finished with these exercises, look at the solutions
in the CORRIG_1.DOC file then go back to the courses.
Good luck! ------------
PIECHOCKI Laurent
8,impasse Bellevue
57980 TENTELING
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