91
CHAPTER 5 CPU ARCHITECTURE
5.1.2 Internal data memory space
The
μ
PD780058 and 780058Y Subseries incorporate the following RAMs.
(1) Internal high-speed RAM
High-speed memory of the following configuration is incorporated:
1,024
×
8 bits (FB00H to FEFFH)
In this area, four banks of general registers, each bank consisting of eight 8-bit registers, are allocated in the
32-byte area FEE0H to FEFFH.
The internal high-speed RAM can also be used as a stack memory area.
(2) Internal buffer RAM
Buffer RAM is allocated to the 32-byte area from FAC0H to FADFH. The internal buffer RAM is used to store
transmit/receive data of serial interface channel 1 (in 3-wire serial I/O mode with automatic transfer/receive
function). If the three-wire serial I/O mode with automatic transfer/receive function is not used, the internal
buffer RAM can also be used as normal RAM. Buffer RAM can also be used as normal RAM.
(3) Internal expansion RAM (
μ
PD780058, 780058Y, 78F0058, 78F0058Y only)
Internal expansion RAM is allocated to the 1,024-byte area from F400H to F7FFH.
5.1.3 Special Function Register (SFR) area
An on-chip peripheral hardware special-function register (SFR) is allocated in the area FF00H to FFFFH. (Refer
to
Table 5-2 Special-Function Register List
in
5.2.3 Special Function Register (SFR)
).
Caution Do not access addresses where the SFR is not assigned.
5.1.4 External memory space
The external memory space is accessible by setting the memory expansion mode register (MM). External memory
space can store program, table data, etc. and allocate peripheral devices.
5.1.5 Data memory addressing
The method to specify the address of the instruction to be executed next, or the address of a register or memory
to be manipulated when an instruction is executed is called addressing.
The address of the instruction to be executed next is addressed by the program counter PC (for details, refer to
5.3 Instruction Address Addressing
).
To address the memory that is manipulated when an instruction is executed, the
μ
PD780058, 780058Y Subseries
is provided with many addressing modes with a high operability. Especially at addresses corresponding to data
memory area, particular addressing modes are possible to meet the functions of the special function registers (SFRs)
and general registers. This area is between FB00H and FFFFH. The data memory space is the entire 64-Kbyte space
(0000H to FFFFH). Figures 5-7 to 5-12 show the data memory addressing modes. For details of each addressing,
refer to
5.4 Operand Address Addressing.