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CHAPTER 5 CPU ARCHITECTURE
5.1.2 Internal data memory space
The
µ
PD78054 and 78054Y subseries units incorporate the following RAMs.
(1) Internal high-speed RAM
The
µ
PD78054 and 78054Y Subseries are provided with the internal high-speed RAM as shown below.
Table 5-3. Internal High-Speed RAM Capacity
Part Number Internal High-Speed RAM
µ
PD78052, 78052Y 512 × 8 bits (FD00H to FEFFH)
µ
PD78053, 78053Y 1024 × 8 bits (FB00H to FEFFH)
µ
PD78054, 78054Y
µ
PD78P054
µ
PD78055, 78055Y
µ
PD78056, 78056Y
µ
PD78058, 78058Y
µ
PD78P058, 78P058Y
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.
(2) Buffer RAM
Buffer RAM is allocated to the 32-byte area from FAC0H to FADFH. The buffer RAM is used to store transmit/
receive data of serial interface channel 1 (in three-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 buffer RAM
can also be used as normal RAM. Buffer RAM can also be used as normal RAM.
(3) Internal expansion RAM (
µ
PD78058, 78058Y, 78P058, 78P058Y only)
Internal expansion RAM is allocated to the 1024-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 5-6. 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.