Figure 2-12 Branch-related addressing modes.

(a) Intrasegment direct

(b) Intrasegment indirect

(c) Intersegment direct

(d) Intersegment indirect

*EA is added to 1610 times the contents of the appropriate segment register.

The addressing modes for indicating branch addresses are graphically defined in Fig. 2-12 and are:

Intrasegment Direct

The effective branch address is the sum of an 8- or 16-bit displacement and the current contents of IP. When the displacement is 8 bits long, it is referred to as a short jump. Intrasegment direct addressing is what most computer books refer to as relative addressing because the displacement is computed "relative" to the IP. It may be used with either conditional or unconditional branching, but a conditional branch instruction can have only an 8-bit displacement.

Intrasegment Indirect

The effective branch address is the contents of a register or memory location that is accessed using any of the above data-related addressing modes except the immediate mode. The contents of IP are replaced by the effective branch address. This addressing mode may be used only in unconditional branch instructions.

Intersegment Direct

Replaces the contents of IP with part of the instruction and the contents of CS with another part of the instruction. The purpose of this addressing mode is to provide a means of branching from one code segment to another.

Intersegment Indirect

Replaces the contents of IP and CS with the contents of two consecutive words in memory that are referenced using any of the above data-related addressing modes except the immediate and register modes.

To demonstrate how indirect branching works with some of the data-related addressing modes, suppose that

Then:

With direct addressing, the effective branch address is the contents of:

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