CHAPTER 3 CPU FUNCTIONSUser’s Manual U16896EJ2V0UD563.4.5 Recommended use of address spaceThe architecture of the V850ES/KE1+ requires that a register that serves as a pointer be secured for addressgeneration when operand data in the data space is accessed. The address stored in this pointer ±32 KB can bedirectly accessed by an instruction for operand data. Because the number of general-purpose registers that can beused as a pointer is limited, however, by keeping the performance from dropping during address calculation when apointer value is changed, as many general-purpose registers as possible can be secured for variables, and theprogram size can be reduced.(1) Program spaceOf the 32 bits of the PC (program counter), the higher 6 bits are fixed to 0, and only the lower 26 bits are valid.Regarding the program space, therefore, a 64 MB space of contiguous addresses starting from 00000000Hunconditionally corresponds to the memory map.To use the internal RAM area as the program space, access the addresses 3FFE000H to 3FFEFFFH (4 KB).(2) Data spaceWith the V850ES/KE1+, it seems that there are sixty-four 64 MB address spaces on the 4 GB CPU addressspace. Therefore, the least significant bit (bit 25) of a 26-bit address is sign-extended to 32 bits and allocatedas an address.(a) Application example of wraparoundIf R = r0 (zero register) is specified for the LD/ST disp16 [R] instruction, a range of addresses 00000000H±32 KB can be addressed by sign-extended disp16. All the resources, including the internal hardware,can be addressed by one pointer.The zero register (r0) is a register fixed to 0 by hardware, and practically eliminates the need for registersdedicated to pointers.Example:μPD703302, 703302YInternal ROM areaOn-chip peripheralI/O areaAccess-prohibitedarea32 KB4 KB24 KB(R = )0 0 0 1 F F F F H0 0 0 0 7 F F F H0 0 0 0 0 0 0 0 HF F F F F 0 0 0 HF F F F E F F F HF F F F 8 0 0 0 HInternal RAMareaF F F F E 0 0 0 HF F F F D F F F H4 KB
