NEC 78K/0 Series - Manual (Page 12)

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User's Manual U12326EJ4V0UM
CHAPTER 1 MEMORY SPACE
1.1 Memory Spaces
The 78K/0 Series product program memory map varies depending on the internal memory capacity. For details
of memory-mapped address area, refer to the user’s manual of each product.
1.2 Internal Program Memory (Internal ROM) Space
Each 78K/0 Series product has internal ROM in the address space. Program and table data, etc. are stored
in the ROM. Normally, this memory space is addressed by the program counter (PC). For details of the internal
ROM space, refer to the user’s manual of each product.
1.3 Vector Table Area
The 64-byte area 0000H to 003FH is reserved as a vector table area. The program start addresses for branch
upon RESET input or interrupt request generation are stored in the vector table area. Of the 16-bit address, the
lower 8 bits are stored at even addresses and the higher 8 bits are stored at odd addresses. For the vector table
area, refer to the user’s manual of each product.
1.4 CALLT Instruction Table Area
The 64-byte area 0040H to 007FH can store the subroutine entry address of a 1-byte call instruction (CALLT).
1.5 CALLF Instruction Entry Area
The 2048-byte area 0800H to 0FFFH can perform a direct subroutine call with a 2-byte call instruction (CALLF).
1.6 Internal Data Memory (Internal RAM) Space
78K/0 Series products incorporate the following RAMs. For details of these RAMs, refer to the user’s manual
of each product.
(1) Internal high-speed RAM
Each 78K/0 Series product incorporates an internal high-speed RAM. In the 32-byte area FEE0H to FEFFH
of these areas, 4 banks of general-purpose registers, each bank consisting of eight 8-bit registers, are
allocated.
The internal high-speed RAM can also be used as a stack memory.
(2) Buffer RAM
There are some products in the 78K/0 Series to which buffer RAM is allocated. This RAM is used to store
the transfer/receive data of serial interface channel 1 (3-wire serial I/O mode with automatic transfer/receive
function). If not used in this mode, the buffer RAM can also be used as an ordinary RAM area.