Based Indexed Addressing; Stack Addressing - NEC mPD780208 Subseries User Manual

3.4.8 Based indexed addressing

[Function]
The B or C register contents specified in an instruction word are added to the contents of the base register, that
is, the HL register pair, and the sum is used to address the memory. The HL, B, and C registers to be accessed
are registers in the register bank specified with the register bank select flag (RBS0 and RBS1).
Addition is performed by expanding the contents of the B or C register as a positive number to 16 bits. A carry
from the 16th bit is ignored. This addressing can be carried out for all the memory spaces.
[Operand format]
[Description example]
In the case of MOV A, [HL+B] (select B register)
Operation code

3.4.9 Stack addressing

[Function]
The stack area is indirectly addressed with the stack pointer (SP) contents.
This addressing method is automatically employed when the PUSH, POP, subroutine call, and return instructions
are executed or the register is saved/reset upon generation of an interrupt request.
Stack addressing can be used to address the internal high-speed RAM area only.
[Description example]
In the case of PUSH DE (save DE register)
Operation code
CHAPTER 3 CPU ARCHITECTURE
Identifier Description
—
[HL+B], [HL+C]
1 0 1 0 1 0 1 1
1 0 1 1 0 1 0
User's Manual U11302EJ4V0UM
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