Motorola M68CPU32BUG Manuel d'utilisateur Page 110

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ASSEMBLER/DISASSEMBLER
M68CPU32BUG/D 4-8
Allowed operators are:
Addition +
Subtraction -
Multiply *
Divide /
Shift left <<
Shift right >>
Bitwise or !
Bitwise and &
The order of evaluation is strictly left to right with no precedence granted to some operators over
others. The only exception is when the user forces the order of precedence via the use of
parentheses.
Possible points of confusion:
Differentiate numbers and registers to avoid confusion. For example:
CLR D0 means CLR.W register D0. On the other hand,
CLR $D0
CLR 0D0
CLR +D0
CLR D0+0 all mean CLR.W memory location $D0.
With the use of asterisk (*) to represent both multiply and program counter,
how does the assembler know when to use which definition?
For parsing algebraic expressions, the order of parsing is
<OPERAND> <OPERATOR> <OPERAND> <OPERATOR>
with a possible left or right parenthesis.
Given the above order, the assembler can distinguish by placement which
definition to use. For example:
*** Means PC * PC
*+* Means PC + PC
2** Means 2 * PC
*&&16 Means PC AND &16
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