Pl2 CORRIG 2.DOC

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EXERCISE CORRECTIONS

NUMBER 2                                 

   

1) Exercise number 1
   -------------

 Here are the listings of the 2 macro instructions 'SAVE' and 'RESTORE'
 that allow to respectively save and restore the 68000's registers.
 
 I will skip the details, it was enough to use the MOVEM instruction.
 The registers will be saved in the system stack by pre-decrement mode
 and restored by post-increment mode. That's all ...

         TEXT

SAVE     MACRO
         movem.l   d0-d7/a0-a6,-(sp)
         ENDM

RESTORE  MACRO
         movem.l   (sp)+,d0-d7/a0-a6
         ENDM

         END




2) Exercise number 2
   -------------  
Here is the listing of the HEXA macro, that allows to display the content 
of its parameter in hexadecimal.

         First we need to successively reach the 8 half-bytes making up
the L-M passed as parameter (1 hex digit = 4 bits).
To do this we use the rotation instruction ROL and place it in
a loop. (LSR also worked...)
We will then mask the 4 least significant bits with AND.L #%1111,dn
to keep only the half-byte to be processed.
The most difficult comes then:
It's now necessary to display the value of this hex digit coded by 4 bits
on screen.
If the digit is <$A (which means <10) this digit will be between 0 and 9. 
By adding $30 to the value of this digit we will get the ascii code
of the digit. (Because the ascii code of '0' is $30: that of '1' is thus
$30+1=$31 etc...)
If the hex digit to be displayed is >9 this digit will be a letter from the
alphabet (from A to F).
By adding $37+$A to the value of this digit we will get the ascii code
of the digit to display. (Because the ascii code of 'A' is $37+$A: that of 'B'
is thus $37+$B=$42 etc...)
It's then enough to display with CCONOUT the ascii code obtained and
to repeat the operation with all the half-bytes of the parameter.

NB: We use the macros SAVE and RESTORE in our HEXA macro to 
-- be able to use all the registers without modifying their content at
   the end of the macro.

   Please note that I'm using LABELS in the HEXA macro.
   Hence the macro can only be used once in a listing because
   the assembler cannot distinguish between two identical labels and at
   each call of a macro, it is fully rewritten...
   You can, however, put the macro in a subroutine to
   be able to call it multiple times...

          TEXT

HEXA      MACRO     $\1              ;macro with 1 parameter
          SAVE                       ;we save the registers so as not
                                     ;to lose their content
          move.l    \1,d1            ;we put the parameter in d1
          moveq     #0,d2            ;initializes the number of shifts
SHIFT     addi.b    #4,d2            ;we add 4 to the number of shifts
          cmpi.b    #36,d2           ;if d2=36=32+4 we finished the 32
          beq       END              ;rotations, in this case -> END
          move.l    d1,d3            ;otherwise we put d1 in d3 and
          rol.l     d2,d3            ;do a rotation of 4 bits
          andi.l    #%1111,d3        ;and we mask these 4 bits as only
                                     ;they must be processed.

; d3 therefore contains the value to be displayed: 0 to 9 or A to F. (because a
; hex digit is coded by 4 bits (see introduction) )

          cmpi.b    #9,d3
          bgt       HEX              ;if d3 >9, go to HEX because we will
                                     ;need to display a letter and no longer a
                                     ;number...

DECIMAL   addi.b    #$30,d3 ;d3=d3+$30 because the ASCII value of 0 is $30
                            ;For example, if d3 is worth 1, we represent it
                            ;by the ascii character $30+1=$31='1', if it
                            ;is 5, by the ascii code $30+5=$35='5', and so
                            ;on for all hex digits <9
          CCONOUT   d3      ;edition of the content of d3

          jmp       SHIFT   ;we re-shift the parameter and continue with
                            ;the next 4 bits in SHIFT

HEX       addi.b    #$37,d3  ;d3=d3+$37 for the hex numbers represented
                             ;by the letters because the ASCII value of A is
                             ;$37+$A. So for exp. if d3 is worth $B, we re-
                             ;present it by the ascii code $37+$B=$42='B'...
          CCONOUT   d3       ;we display the letter (from A to F)

          jmp       SHIFT    ;we re-shift the parameter and continue with
                             ;the next 4 bits in SHIFT

END       RESTORE            ;when we are done with all the 32 bits,
                             ;we restore the stacked registers
          ENDM

          END
     


3) Exercise number 3
   -------------
Here is the correction of the 'BINARY' macro.

To reach the 32 bits of the parameter and to display them on the screen,
we use the instruction LSL.L #1, parameter in a loop and depending on
the value of the shift out bit, we display a '1' (active bit) or a '0' (extinguished
bit).
The corresponding conditional branch instruction can for example be
bCC (Which tests if the C bit of the CCR is zero: LSL copies the shifted out
bit into the C bit of the CCR)
To display the '1' or the '0', we use the CCONOUT #'1' or
CCONOUT #'0' macro.

NB:Same remarks as for the HEXA macro concerning the use of labels
-- in the 'BINARY' macro.

     
          TEXT     

BINARY    MACRO     $\1      ;MACRO with 1 parameter
          SAVE               ;registers saved
          move.L    \1,d1    ;the parameter in d1
          move      #31,d3   ;loop counter for shifts

LOOK      move      #'0',d0  ;d0 contains the ascii code of 0
          lsl.l     #1,d1    ;shift of one bit of d1: Copy of the bit into
                             ;the C code of the CCR
          bcc       ZERO     ;if the bit is zero (C=0): go to 'zero'
          move      #'1',d0  ;otherwise d0 contains the ascii code of '1'
ZERO      CCONOUT   d0       ;we display the content of d0 (0 or 1)
          dbf       d3,LOOK  ;we continue with the other 31 bits
          RESTORE            ;we restore the registers
          ENDM               ;done...

          END



4) Exercise number 4:
   --------------

 Here is the listing of the program that formats a floppy disk.
 
  It was simply necessary to properly use the FLOPFMT function of the Gemdos
 and put it in a loop to be able to vary the number of the track to format.

 To ask for execution confirmation from the program's user,
 we display an alert message with PRINTLINE, we wait for him to press
 a keyboard key (with 'WAIT') and we test the ascii code of
 the selected key. (value which returns in d0)
 If this key is 'F' we format the floppy, otherwise we exit the program
 with the TERM macro (TERM function of the Gemdos).

 If an error occurs during formatting (d0 negative after FLOPFMT),
 we display the error code in DECIMAL.
 We will first need to make the digit to process positive with NEG  dn.
 The digit to process (the error code) will thus be a positive number 
 and less than 100 (see the Gemdos error codes).
 We perform a division by 10 of this digit to get the tens digit
 with DIVU #10,dn.
 The quotient returns in the low weight word of dn: it's the tens digit, we display it
 by adding $30 to obtain an ascii code (with CCONOUT).
 The remainder is in the high weight word of dn: It represents the
 units digit of the error code. We SWAP dn and also display it.
     
 When the formatting is finished, we display a message indicating that
 everything is OK.
  
 Remark:
 ---------
     BE CAREFUL, our program will format the disk correctly, but if
     you look at the disk information using the 'INFORMATION' option of the GEM desktop, it will indicate that there
     remain 0 bytes free even though there are also 0 used...
     This is explained by the fact that we haven't initialized the
     BOOT SECTOR of the floppy: It will therefore not be writable because
     it contains all the necessary information for disk operations...

 NB: Those who don't have PROFIMAT and who want (must!) set
 -- the buffer for FLOPFMT to an EVEN address should not write
    the DIRECTIVE: 'ALIGN.W' in the BSS area.
    For METACOMCO, there is an equivalent DIRECTIVE: CNOP 0,2
    For DEVPAC ST: it's the EVEN directive.
    The others will assemble the listing and if it doesn't work, it's because
    the buffer for FLOPFMT is not at an even address.
    It will then be sufficient to reserve 1 BYTE just in front of the buffer: it
    will thus move from an odd address to an even address (odd+1).
  


          TEXT

          INCLUDE   "INIT_TOS.L"
          INCLUDE   "MACROS.L"


          SETBLOCK

          PRINTLINE ATTENTION   ;the alert message   

          WAIT                  ;waiting for a key:ascii code in d0
          CMPI.B    #'F',d0     ;d0='F' ?
          BEQ       FORMAT      ;if so, FORMAT
          CMPI.B    #'f',d0     ;d0='f' ?
          BEQ       FORMAT      ;if so, FORMAT
          TERM                  ;otherwise exit

FORMAT    SUPER                 ;SUPERVISOR mode 
                                
          clr.l     d0

LOOP      movem.l   d0,-(sp)          ;we save just d0
          move.w    #$e5e5,-(sp)      ;virgin
          move.l    #$87654321,-(sp)  ;magic word
          move.w    #1,-(sp)          ;interleave
          move.w    #0,-(sp)          ;side
          move.w    d0,-(sp)          ;d0=different tracks
          move.w    #9,-(sp)          ;number of sectors per track
          move.w    #0,-(sp)          ;drive A
          clr.l     -(sp)             ;L-M=0
          pea       BUFFER            ;buffer address
          move.w    #$a,-(sp)         ;Flopfmt
          trap      #14
          add.l     #26,sp            ;update SP  
          tst       d0
          bmi       ERROR             ;If d0 is negative: error
          movem.l   (sp)+,d0          ;we restore d0
          addi.b    #1,d0             ;we increment the track number
          cmpi.b    #80,d0            ;have we the 80 tracks ?
          bne       LOOP

          PRINTLINE OK                ;no problem, OK
CONTINUE  WAIT                        ;waiting for a key
          USER                        ;we return to USER mode
          TERM                        ;-> exit

ERROR     move      d0,d5        ;we save d0 in d5 because d0 will be modified
          PRINTLINE PROBLEM
          neg       d5           ;d5 becomes positive

;         DECIMAL display of d5

          divu      #10,d5       ;tens digit in the low word of d5
          add       #$30,d5      ;digit=ascii code
          CCONOUT   d5           ;we display it
          swap      d5           ;low word of d5=remainder of division=digit
                                 ;units of d5
          add       #$30,d5      ;digit=ascii code
          CCONOUT   d5           ;we display it
          jmp       CONTINUE     ;--> end


          DATA

ATTENTION DC.B      27,'E','DANGER! This program FORMATS the floppy disk,'
          DC.B      ' insert a BLANK disk then',10,13,'press'
          DC.B      ' [F] to FORMAT the floppy disk...'
          DC.B      ' (Or another key to EXIT!)',7,0

OK        DC.B      27,'E','No error: OK...',0

PROBLEM   DC.B      27,'E',7,'ERROR code:-',0


          BSS

          DS.B      20000    ;buffer upstream of the new STACK
PILE      DS.B      1        ;formatting requires a lot of space...
          ALIGN.W            ;SPECIFIC to PROFIMAT !!!!!
BUFFER    DS.B      10000    ;buffer for formatting (EVEN address)
SAUV_SP   DS.L      1        ;buffer for SUPER and USER

          END



5) Exercise number 5
   -------------

 Here is the program that replays the sounds created with PRO SOUND DESIGNER.

 The program will wait until a key is pressed on the keyboard then it
 tests it (Macro 'WAIT' from gemdos, return of the code and the scancode in
 d0).
 Function keys have no ascii code but all have a
 SCANCOD that differentiates them.
 If the low byte of d0 contains an ascii code (d0.w different
 from 0), we exit the program because it means we have pressed a key other
 than one of the 10 function keys.

 You then had to find the different scancodes of function keys
 to be able to use them here.
 For that, you just had to write the following program,
 
     TEXT 

     INCLUDE  "MACROS.L"
     
AA   WAIT                ;waiting for a key
     SWAP   d0           ;low weight byte of d0 = scancode
     and.l  #$FF,d0      ;we keep only the low byte of
                         ;this word (which is the SCANCODE)           
     HEXA   d0           ;display in HEXA the scancode
     WAIT                ;waiting for a key
     CCONOUT   #27
     CCONOUT   #'E'      ;we clear the screen
     jmp       AA        ;and we start again

     END

  then to assemble it, to execute it and to press on the function keys to note their SCANCODES.

  The rest of the program must identify the different scancodes of
  the function keys and play a sound.
  To test the values of the scancode of the pressed key, we compare
  the value of the scancode entered with the values of the 10 scancodes of the function keys that we have placed in the DATA area.
  At the same time, we vary the value of an 'an' address register
  which points to the different sound addresses.
  If a scancode is identified, we play the sound pointed by 'an' by
  providing it as a parameter to the macro 'DOSOUND', otherwise we increment
  address registers (mode (an)+) pointing to the DATAs that represent
  the scancodes and sound addresses.
  If no scancode is finally recognized, we restart the keyboard test from
  the beginning of the program.
    
      The data defining the sounds are in the file 
 PROSOUND.DAT, just include it in the DATA zone in the listing.


 NB:I'm modifying the value of a SYSTEM VARIABLE in this listing (with
 -- move.b  #0,$484) this with the purpose of stopping the 'BEEP' that is
    heard when pressing a key in order not to disturb
    the replayed sound.
    I will soon talk about the SYSTEM VARIABLES...

  

               TEXT

               INCLUDE       "INIT_TOS.L"
               INCLUDE       "MACROS.L"

               SETBLOCK

               SUPER                           ;SUPERVISOR mode

               PRINTLINE     message           ;text
               move.b        #0,$484           ;system variable (putting
                                               ;0 removes repetition and
                                               ;beep of the keys)

TEST           WAIT                            ;waiting for a key
                                               ;:CODE in d0
               tst.b         d0                ;if ascii code different from
               bne           STP               ;0, then SToP, otherwise
               swap          d0                ;low word d0
                                               ;becomes the SCANCODE

               lea           FUNCT,a0          ;a0=address of SCANCODES
               lea           VECTOR,a1         ;a1=address of sound
                                               ;address of VECTOR

SONGS          cmp.b         (a0)+,d0          ;compare SCANCODE of the
                                               ;pressed key (d0) to
                                               ;those in the table DC.B .
               move.l        (a1)+,a5          ;Puts the address pointed by
                                               ;a1 in a5
               beq           SOUND             ;if CMP=yes, go play the 
                                               ;sound pointed by a5
               addq.b        #1,d1             ;otherwise add 1 to d1
               cmpi.b        #9,d1             ;d1=9 ?
               beq           TEST              ;then no more scancodes
                                               ;and we return to 'TEST'
               jmp           SONGS             ;otherwise we increment a0
                                               ;and a1


SOUND          DOSOUND       a5                ;Dosound the sound pointed by
                                               ;a5
               jmp           TEST              ;then we return to 'TEST'

STP            USER                            ;USER mode
               TERM                            ;we exit


               DATA

MESSAGE        DC.B       27,'E','Here are some PRO SOUND DESIGNER sounds'
               DC.B       ', press the Function keys:'
               DC.B       '(Or another key to exit)',7,0

VECTOR         DC.L          sound0,sound1,sound2,sound3,sound4,sound5
               DC.L          sound6,sound7,sound8,sound9
               ;addresses of the 10 sounds.

FUNCT           DC.B          $3B,$3C,$3D,$3E,$3F,$40,$41,$42,$43,$44
               ;Function keys scancodes (F1->F10)

; Data defining PRO SOUND DESIGNER sounds

sound0    DC.B  0,214
          DC.B  1,0
          DC.B  2,215
          DC.B  3,0
          DC.B  4,215
          DC.B  5,0
          DC.B  7,248
          DC.B  8,16
          DC.B  9,16
          DC.B  10,16
          DC.B  11,32
          DC.B  12,73
          DC.B  13,0
          DC.B  129,2
          DC.B  0,0
          DC.B  255,0
sound1    DC.B  0,24
          DC.B  1,1
          DC.B  2,25
          DC.B  3,1
          DC.B  4,23
          DC.B  5,1
          DC.B  7,248
          DC.B  8,16
          DC.B  9,16
          DC.B  10,16
          DC.B  11,32
          DC.B  12,73
          DC.B  13,0
          DC.B  129,2
          DC.B  0,0
          DC.B  255,0
sound2    DC.B  0,156
          DC.B  1,1
          DC.B  2,156
          DC.B  3,1
          DC.B  4,156
          DC.B  5,1
          DC.B  7,248
          DC.B  8,16
          DC.B  9,16
          DC.B  10,16
          DC.B  11,32
          DC.B  12,73
          DC.B  13,0
          DC.B  129,2
          DC.B  0,0
          DC.B  255,0
sound3    DC.B  0,22
          DC.B  1,2
          DC.B  2,21
          DC.B  3,2
          DC.B  4,23
          DC.B  5,2
          DC.B  7,248
          DC.B  8,16
          DC.B  9,16
          DC.B  10,16
          DC.B  11,32
          DC.B  12,73
          DC.B  13,0
          DC.B  129,2
          DC.B  0,0
          DC.B  255,0
sound4    DC.B  0,55
          DC.B  1,3
          DC.B  2,59
          DC.B  3,3
          DC.B  4,57
          DC.B  5,3
          DC.B  7,248
          DC.B  8,16
          DC.B  9,16
          DC.B  10,16
          DC.B  11,32
          DC.B  12,73
          DC.B  13,0
          DC.B  129,2
          DC.B  0,0
          DC.B  255,0
sound5    DC.B  0,235
          DC.B  1,3
          DC.B  2,234
          DC.B  3,3
          DC.B  4,232
          DC.B  5,3
          DC.B  7,248
          DC.B  8,16
          DC.B  9,16
          DC.B  10,16
          DC.B  11,32
          DC.B  12,73
          DC.B  13,0
          DC.B  129,2
          DC.B  0,0
          DC.B  255,0
sound6    DC.B  0,70
          DC.B  1,5
          DC.B  2,72
          DC.B  3,5
          DC.B  4,71
          DC.B  5,5
          DC.B  7,248
          DC.B  8,16
          DC.B  9,16
          DC.B  10,16
          DC.B  11,32
          DC.B  12,73
          DC.B  13,0
          DC.B  129,2
          DC.B  0,0
          DC.B  255,0
sound7    DC.B  0,84
          DC.B  1,7
          DC.B  2,84
          DC.B  3,7
          DC.B  4,84
          DC.B  5,7
          DC.B  7,248
          DC.B  8,16
          DC.B  9,16
          DC.B  10,16
          DC.B  11,32
          DC.B  12,73
          DC.B  13,0
          DC.B  129,2
          DC.B  0,0
          DC.B  255,0
sound8    DC.B  0,175
          DC.B  1,0
          DC.B  2,193
          DC.B  3,4
          DC.B  4,20
          DC.B  5,6
          DC.B  7,254
          DC.B  8,16
          DC.B  9,16
          DC.B  10,16
          DC.B  11,32
          DC.B  12,73
          DC.B  13,0
          DC.B  129,0
          DC.B  93,63
          DC.B  255,0
sound9    DC.B  0,175
          DC.B  1,0
          DC.B  2,193
          DC.B  3,4
          DC.B  4,232
          DC.B  5,4
          DC.B  7,254
          DC.B  8,16
          DC.B  9,16
          DC.B  10,16
          DC.B  11,32
          DC.B  12,73
          DC.B  13,0
          DC.B  129,0
          DC.B  80,88
          DC.B  255,0


               BSS

               DS.B          40000             ;for SETBLOCK
STACK          DS.B          1
SAVE_SP        DS.L          1                 ;for SUPER/USER

               END