CHAPTER 3 CPU FUNCTION
User’s Manual U12688EJ4V0UM00
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3.4.7 Recommended use of address space
The architecture of the V850E/MS1 requires that a register that serves as a pointer be secured for address
generation when accessing the operand data in the data space. An instruction can be used to directly access
operand data at the address in this pointer register ±32 KB. However, the general-purpose registers that can be used
as a pointer register are limited. Therefore, by minimizing the deterioration of address calculation performance when
changing the pointer value, the number of usable general-purpose registers for handling variables is maximized, and
the program size can be saved.
To enhance the efficiency of using the pointer in connection with the memory map of the V850E/MS1, the following
points are recommended:
(1) Program space
Of the 32 bits of the PC (program counter), the higher 6 bits are fixed to 0, and only the lower 26 bits are valid.
Therefore, a contiguous 64 MB space, starting from address 00000000H, unconditionally corresponds to the
memory map of the program space.
(2) Data space
For the efficient use of resources using the wrap-around feature of the data space, the continuous 16 MB
address spaces 00000000H to 00FFFFFFH and FF000000H to FFFFFFFFH of the 4 GB CPU are used as the
data space. With the V850E/MS1, the 64 MB physical address space is seen as 64 images in the 4 GB CPU
address space. The highest bit (bit 25) of this 26-bit address is assigned as address sign-extended to 32 bits.
Содержание V850E/MS1 UPD703100
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