Addressing Modes Notation

The notation is also called the Register Transfer Language (RTL). In this notation the registers are denoted by their names, while when between brackets, so as [D0], means the contents of the register D0. Therefore if is written [D0]=7, means that the content of D0 is equal to 7.
The base number is denoted by a prefix. No prefix means decimal base, a percent prefix (%) means binary, and a dollar ($) prefix means hexadecimal. To represent a 32-bit number using hexadecimal base is necessary to write eight characters, for example, $FFFF FFFF. As noted, for purposes of style is left a space between the last four significant numbers. In an assembly program no blank space should be left between hexadecimal numbers.
The backwards arrow (<-) indicates a transfer of information. For example:   [D0] <- 7     ( put 7 into register D0)

The following symbols are used in the definition of addressing modes:
 
 

Symbol Meaning
M Location (i.e., address) Min the main store
Ai Address register (i= 0 to 7)
Di Data register (i= 0 to 7)
Xi General register i (Xi may be an address or data register)
[M] The contents of memory location M (M is used only to represent a general memory location.
[X] The contents of register X (X may be an address or a data register)
[D,(0:7)] Bits zero to seven of register Di
<> Enclose a parameter required by an expression
ea The effective address of an operand
[M(ea)] The contents of a memory location whose effective address is ea
d8 An 8-bit signed offset (a constant in the range -128 to 127)
d16 A 16-bit signed offset (a constant in the range -32K to 32K)
d32 A 32-bit signed offset (a constant in the range -2G to 2G)

As an example of the use of this notation, here is the ADD instruction.
The instruction ADD <source>, <destination>  and it has the effect:
[destination] <- [destination] + [source]
In RTL terms, the assembly language instruction ADD <s>,<d> is defined as [M(d)] <- [M(s)] + [M(d)]. That is, the content of  "source" is added to the content of "destination" and the result is transferred to the "destination".

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