NEC switch - Manual (Page 37)

CHAPTER 3 CPU ARCHITECTURE
User’s Manual U12978EJ3V0UD
37
3.1.1 Internal program memory space
The internal program memory space stores programs and table data. This space is usually addressed by the
program counter (PC).
The following areas are allocated to the internal program memory space.
(1) Vector table area
A 26-byte area of addresses 0000H to 0019H is reserved as a vector table area. This area stores program start
addresses to be used when branching by RESET input or interrupt request generation. Of a 16-bit program
address, the lower 8 bits are stored in an even address, and the higher 8 bits are stored in an odd address.
Table 3-1. Vector Table
Vector Table Address Interrupt Request Vector Table Address Interrupt Request
0000H RESET input 000EH INTUSBRE
0004H INTWDT 0010H INTP0
0006H INTUSBTM 0012H INTCSI10
0008H INTUSBRT 0014H INTTM00
000AH INTUSBRD 0016H INTTM01
000CH INTUSBST 0018H INTKR00
(2) CALLT instruction table area
The subroutine entry address of a 1-byte call instruction (CALLT) can be stored in a 64-byte area of addresses
0040H to 007FH.
3.1.2 Internal data memory (internal high-speed RAM) space
An internal high-speed RAM is incorporated in the area between FE00H and FEFFH.
The internal high-speed RAM is also used as a stack.
3.1.3 Special function register (SFR) area
Special function registers (SFRs) of on-chip peripheral hardware are allocated to an area of FF00H to FFFFH
(see Table 3-2).