Zilog Z08470 - Manual (Page 46)

Z80 CPU Instructions UM008007-0715
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Z80 CPU
User Manual
Addressing Modes
Most of the Z80 instructions operate on data stored in internal CPU registers, external
memory, or in the I/O ports. Addressing refers to how the address of this data is generated
in each instruction. This section is a brief summary of the types of addressing used in the
Z80 CPU while subsequent sections detail the type of addressing available for each
instruction group.
Immediate Addressing
In the Immediate Addressing Mode, the byte following the op code in memory contains
the actual operand, as shown in Figure 25.
An example of this type of instruction is to load the Accumulator with a constant, in which
the constant is the byte immediately following the op code.
Immediate Extended Addressing
This mode is an extension of immediate addressing in that the two bytes following the op
codes are the operand, as shown in Figure 26.
An example of this type of instruction is to load the HL register pair (16-bit register) with
16 bits (two bytes) of data.
Figure 25. Immediate Addressing Mode
Figure 26. Immediate Extended Addressing Mode
One or Two Bytes
D7 D0
Op Code
Op Code
One or Two Bytes
low-order
high-order
Op Code
Op Code
Op Code