Indirect Register Addressing (Ir) - ZiLOG Z8 PLUS User Manual

4-Bit Working
Registers
Two Operand
Instruction
(Example)
In 4-bit Register Addressing (see Figure 2-2), the destination and/or source addresses point to the Working
Register within the current Working Register Group. This 4-bit address is combined with the Register Pointer
to form the actual 12-bit address of the affected register.

INDIRECT REGISTER ADDRESSING (IR)

In the Indirect Register Addressing Mode, the contents of the specified register are equivalent to the address
of the operand (see Figure 2-3 and Figure 2-4).
Depending upon the instruction selected, the specified register contents points to a Register or Program
Memory location.
When accessing program memory, register pairs or Working Register pairs are used to hold the 16-bit
addresses.
Program Memory
dst src
OpCode
Figure 2-2. 4-Bit Register Addressing
Points to
One Register
in the
Register
File
.75
P Â
Register File
RP
Operand
Operand
Points to
Origin of
Working
Register
Group