ST NEWS Atari Multimedia Disk Magazine

ASSEMBLY LANGUAGE COURSE - PART V by Mark van den Boer

Logical Operations

Instruction:   AND
Syntax:        AND <ea>,Dn
               AND Dn,<ea>
Data sizes:    byte, word, long
Condition codes affected:
               X    not affected
               N    set to the most significant bit of the result
               Z    set if the result is zero, cleared otherwise
               V,C  always cleared

Addressing modes:
Source: (destination is Dn)
          Dn
          (An)
          (An)+
          -(An)
          w(An)
          b(An,Rn)
          w
          l
          w(PC)
          b(PC,Rn)
Destination: (source is Dn)
          (An)
          (An)+
          -(An)
          w(An)
          b(An,Rn)
          w
          l
Function: Perform   a   boolean  bitwise  AND   from   source   to
          destination.
Examples:
Instruction              Before         After
AND.B d0,d1              d0=33333333    d0=33333333
                         d1=ffffffff    d1=ffffffcc
AND.W d0,d1              d0=33333333    d0=33333333
                         d1=ffffffff    d1=ffffcccc
AND.L d0,d1              d0=33333333    d0=33333333
                         d1=ffffffff    d1=cccccccc

Instruction:   ANDI
Syntax:        ANDI #,<ea>
Data sizes:    byte, word, long
Condition codes affected:
               X    not affected
               N    set to the most significant bit of the result
               Z    set if the result is zero, cleared otherwise
               V,C  always cleared

Addressing modes:
Destination:
          Dn
          (An)
          (An)+
          -(An)
          w(An)
          b(An,Rn)
          w
          l
          CCR, SR
Function: Perform   a   boolean  bitwise  AND   from   source   to
          destination.
Examples:
Instruction              Before         After
ANDI.B #7,d0             d0=33333333    d0=33333330
ANDI.W #$ff00,SR         SR=ffff        SR=ff00

Instruction:   EOR
Syntax:        EOR Dn,<ea>
Data sizes:    byte, word, long
Condition codes affected:
               X    not affected
               N    set to the most significant bit of the result
               Z    set if the result is zero, cleared otherwise
               V,C  always cleared
Addressing modes:
Destination:
          Dn
          (An)
          (An)+
          -(An)
          w(An)
          b(An,Rn)
          w
          l

Function: Perform  a bitwise exclusive or from source to  destina-
          tion.  You  will notice that this instruction  can  only
          take a data register as the source,  unlike the AND  and
          OR  instructions.  I  think the designers of  the  68000
          should have mode addressing modes more orthogonal.
Examples:
Instruction              Before         After
EOR.L d0,d1              d0=ffffffff    d0=ffffffff
                         d1=f0f0f0f0    d1=0f0f0f0f

Instruction:   EORI
Syntax:        EORI #,<ea>
Data sizes:    byte, word, long
Condition codes affected:
               X    not affected
               N    set to the most significant bit of the result
               Z    set if the result is zero, cleared otherwise
               V,C  always cleared

Addressing modes:
Destination:
          Dn
          (An)
          (An)+
          -(An)
          w(An)
          b(An,Rn)
          w
          l
          CCR, SR
Function: Perform   a   bitwise  exclusive  or  from   source   to
          destination.
Examples:
Instruction              Before         After
EORI.B #$ff,d0           d0=33333330    d0=333333cf
EORI.W #$00ff,SR         SR=ff32        SR=ffcd

Instruction:   NOT
Syntax:        NOT <ea>
Data sizes:    byte, word, long
Condition codes affected:
               X    not affected
               N    set to the most significant bit of the result
               Z    set if the result is zero, cleared otherwise
               V,C  always cleared
Addressing modes:
Destination:
          Dn
          (An)
          (An)+
          -(An)
          w(An)
          b(An,Rn)
          w
          l
Function: Perform a bitwise not to the effective address  operand.
          Note that NOT.W d0 is the same as EORI.W #$ffff,d0.

Examples:
Instruction              Before         After
NOT.B #$ff,d0            d0=ffffff78    d0=ffffff87

Instruction:   OR
Syntax:        OR <ea>,Dn
               OR Dn,<ea>
Data sizes:    byte, word, long
Condition codes affected:
               X    not affected
               N    set to the most significant bit of the result
               Z    set if the result is zero, cleared otherwise
               V,C  always cleared

Addressing modes:
Source: (destination is Dn)
          Dn
          (An)
          (An)+
          -(An)
          w(An)
          b(An,Rn)
          w
          l
          w(PC)
          b(PC,Rn)
Destination: (source is Dn)
          (An)
          (An)+
          -(An)
          w(An)
          b(An,Rn)
          w
          l
Function: Perform a boolean bitwise OR from source to destination.

Examples:
Instruction              Before         After
OR.B d0,d1               d0=ffffffff    d0=ffffffff
                         d1=33333333    d1=333333ff
OR.W d0,d1               d0=ffffffff    d0=ffffffff
                         d1=33333333    d1=3333ffff
OR.L d0,d1               d0=ffffffff    d0=ffffffff
                         d1=33333333    d1=ffffffff

Instruction:   ORI
Syntax:        ORI #,<ea>
Data sizes:    byte, word, long
Condition codes affected:
               X    not affected
               N    set to the most significant bit of the result
               Z    set if the result is zero, cleared otherwise
               V,C  always cleared

Addressing modes:
Destination:
          Dn
          (An)
          (An)+
          -(An)
          w(An)
          b(An,Rn)
          w
          l
          CCR, SR
Function: Perform  a boolean bitwise OR from source  to  destina-
          tion.
Examples:
Instruction              Before         After
ORI.B #7,d0               d0=33333330    d0=33333333
ORI.W #$00ff,SR           SR=ff00        SR=ffff

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The text of the articles is identical to the originals like they appeared in old ST NEWS issues. Please take into consideration that the author(s) was (were) a lot younger and less responsible back then. So bad jokes, bad English, youthful arrogance, insults, bravura, over-crediting and tastelessness should be taken with at least a grain of salt. Any contact and/or payment information, as well as deadlines/release dates of any kind should be regarded as outdated. Due to the fact that these pages are not actually contained in an Atari executable here, references to scroll texts, featured demo screens and hidden articles may also be irrelevant.

MC 68000 Part V