CHAPTER 3 CPU FUNCTION
User’s Manual U12688EJ4V0UM00
78
3.4.3 Wrap-around of CPU address space
(1) Program space
Of the 32 bits of the PC (program counter), the higher 6 bits are set to 0, and only the lower 26 bits are valid.
Even if a carry or borrow occurs from bit 25 to 26 as a result of branch address calculation, the higher 6 bits
ignore the carry or borrow.
Therefore, the lower-limit address of the program space, address 00000000H, and the upper-limit address
03FFFFFFH become contiguous addresses. Wrap-around refers to the situation that the lower-limit address
and upper-limit address become contiguous like this.
Caution
No instruction can be fetched from the 4 KB area of 03FFF000H to 03FFFFFFH because this
area is defined as the peripheral I/O area. Therefore, do not execute any branch address
calculation in which the result will reside in any part of this area.
03FFFFFEH
03FFFFFFH
00000000H
00000001H
Program space
Program space
(+) direction
( ) direction
(2) Data space
The result of an operand address calculation that exceeds 32 bits is ignored.
Therefore, the lower-limit address of the program space, address 00000000H, and the upper-limit address
FFFFFFFFH are contiguous addresses, and the data space is wrapped around at the boundary of these
addresses.
FFFFFFFEH
FFFFFFFFH
00000000H
00000001H
Data space
Data space
(+) direction
( ) direction
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