uPD789074 Subseries 8-Bit Single-Chip Microcontrollers UD - Home

CHAPTER 3 CPU ARCHITECTURE3.1.1 Internal program memory spaceThe internal program memory space stores programs and table data. This space is usually addressed by theprogram counter (PC).Products in the µPD789074 Subseries provide the following internal ROM (or flash memory) containing thefollowing capacities.Table 3-1. Internal ROM CapacityPart NumberInternal ROMµPD789071µPD789072µPD789074Mask ROMStructureCapacity2,048 × 8 bits4,096 × 8 bits8,192 × 8 bitsµPD78F9076 Flash memory 16,384 × 8 bitsThe following areas are allocated to the internal program memory space.(1) Vector table areaThe 24-byte area of addresses 0000H to 0017H is reserved as a vector table area. This area storesprogram start addresses to be used when branching by RESET input or interrupt request generation. Of a16-bit program address, the lower 8 bits are stored in an even address, and the higher 8 bits are stored in anodd address.Table 3-2. Vector TableVector Table Address Interrupt Request Vector Table Address Interrupt Request0000H RESET input 000CH INTSR20/INTCSI200004H INTWDT 000EH INTST200006H INTP0 0014H INTTM800008H INTP1 0016H INTTM90000AHINTP2(2) CALLT instruction table areaThe subroutine entry address of a 1-byte call instruction (CALLT) can be stored in the 64-byte area ofaddresses 0040H to 007FH.3.1.2 Internal data memory (internal high-speed RAM) spaceThe µPD789074 Subseries provides 256-byte internal high-speed RAM.The internal high-speed RAM can also be used as a stack memory.3.1.3 Special function register (SFR) areaSpecial function registers (SFRs) of on-chip peripheral hardware are allocated to the area of FF00H to FFFFH(see Table 3-3).User’s Manual U14801EJ3V1UD 41