Pl EXOS 1.DOC
------------------------- EXERCISES I ------------------------- - Solutions to the exercises proposed in this file are present in the file: CORRIG_1.DOC ------------ You just need to note the exercise number whose answer you want to know. ------------------ 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: -------- 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? ----------------- 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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