Internal Data Memory (Internal High-Speed Ram) Space; Special Function Register (Sfr) Area; Data Memory Addressing - NEC mPD789101 User Manual

4.1.2 Internal data memory (internal high-speed RAM) space

The µ PD789134 Subseries provides a 256-byte internal high-speed RAM.
The internal high-speed RAM can also be used as a stack memory.

4.1.3 Special function register (SFR) area

Special function registers (SFRs) of on-chip peripheral hardware are allocated to the area of FF00H to FFFFH (refer
to Table 4-3).

4.1.4 Data memory addressing

The µ PD789134 Subseries provides a variety of addressing modes which take account of memory manipulability,
etc. Especially at addresses corresponding to data memory area (FE00H to FEFFH), particular addressing modes
are possible to meet the functions of the special function registers (SFRs) and general registers. Figures 4-5 through
4-8 show the data memory addressing modes.
Figure 4-5. Data Memory Addressing ( µ PD789101, 789111, 789121, 789131)
FFFFH
Special function registers (SFRs)
FF20H
FF1FH
FF00H
FEFFH
Internal high-speed RAM
FE20H
FE1FH
FE00H
FDFFH
0800H
07FFH
Internal ROM
2,048 × 8 bits
0000H
52
CHAPTER 4 CPU ARCHITECTURE
SFR addressing
256 × 8 bits
256 × 8 bits
Reserved
User's Manual U13045EJ2V0UM00
Short direct
addressing
Direct addressing
Register indirect
addressing
Based addressing