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3.4.7 Recommended use of address space
The architecture of the V850/SA1 requires that a register that serves as a pointer be secured for address
generation in operand data accessing for data space. The address in this pointer register ±32 Kbytes can be
accessed directly from instruction. However, general register used as a pointer register is limited. Therefore, by
minimizing the deterioration of address calculation performance when changing the pointer value, the number of
usable general registers for handling variables is maximized, and the program size can be saved because instructions
for calculating pointer addresses are not required.
To enhance the efficiency of using the pointer in connection with the memory map of the V850/SA1, the following
points are recommended:
(1) Program space
Of the 32 bits of the PC (program counter), the higher 8 bits are fixed to "0", and only the lower 24 bits are valid.
Therefore, a contiguous 16-Mbyte space, starting from address 00000000H, unconditionally corresponds to the
memory map of the program space.
(2) Data space
For the efficient use of resources to be performed through the wrap-around feature of the data space, the
continuous 8-Mbyte address spaces 00000000H to 007FFFFFH and FF800000H to FFFFFFFFH of the 4-Gbyte
CPU are used as the data space. With the V850/SA1, 16-Mbyte physical address space is seen as 256 images
in the 4-Gbyte CPU address space. The highest bit (bit 23) of this 24-bit address is assigned as address sign-
extended to 32 bits.
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CHAPTER 3
CPU FUNCTIONS
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