Autodecrement Mode Similar to the autoincrement, the autodecrement mode uses a register to hold the address of the operand. However, in this case the content of the autodecrement register is first decremented and the new content is used as the effective address of the operand. In order to reflect the fact that the content of the autodecrement register is decremented before accessing the operand, a (2) is included before the indirection parentheses. Consider, for example, the instruction LOAD (Rauto), Ri. This instruction decrements the content of the register Rauto and then uses the new content as the effective address of the operand that is to be loaded into register Ri. Figure 2.11 illustrates the autodecrement addressing mode.
The seven addressing modes presented above are summarized in Table 2.2. In each case, the table shows the name of the addressing mode, its definition, and a generic example illustrating the use of such mode.
In presenting the different addressing modes we have used the load instruction
for illustration. However, it should be understood that there are other types of instructions in a given machine. In the following section we elaborate on the different types of instructions that typically constitute the instruction set of a given
machine.
The seven addressing modes presented above are summarized in Table 2.2. In each case, the table shows the name of the addressing mode, its definition, and a generic example illustrating the use of such mode.
In presenting the different addressing modes we have used the load instruction
for illustration. However, it should be understood that there are other types of instructions in a given machine. In the following section we elaborate on the different types of instructions that typically constitute the instruction set of a given
machine.
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