CHAPTER 3 CPU FUNCTIONS
User’s Manual U13850EJ4V0UM
88
(3) Internal peripheral I/O area
A 4 KB area of addresses FFF000H to FFFFFFH is reserved as an internal peripheral I/O area. The V850/SB1
and V850/SB2 are provided with a 1 KB area of addresses FFF000H to FFF3FFH as a physical internal
peripheral I/O area, and its image can be seen on the rest of the area (FFF400H to FFFFFFH).
Peripheral I/O registers associated with the operation mode specification and the state monitoring for the internal
peripherals are all memory-mapped to the internal peripheral I/O area. Program fetches are not allowed in this
area.
Figure 3-18. Internal Peripheral I/O Area
xxFFFFFFH
xxFFFC00H
xxFFFBFFH
xxFFF800H
xxFFF7FFH
xxFFF400H
xxFFF3FFH
xxFFF000H
Image
Image
Image
Physical internal
peripheral I/O
3FFH
000H
Image
Peripheral I/O
Cautions 1. The least significant bit of an address is not decoded since all registers reside on an even
address. If an odd address (2n + 1) in the peripheral I/O area is referenced (accessed in
byte units), the register at the next lowest even address (2n) will be accessed.
2. If a register that can be accessed in byte units is accessed in half-word units, the higher 8
bits become undefined, if the access is a read operation. If a write access is made, only
the data in the lower 8 bits is written to the register.
3. If a register with n address that can be accessed only in half-word units is accessed in
word units, the operation is replaced with two half-word operations. The first operation
(lower 16 bits) accesses to the register with n address and the second operation (higher
16 bits) accesses to the register with n + 2 address.
4. If a register with n address that can be accessed in word units is accessed with a word
operation, the operation is replaced with two half-word operations. The first operation
(lower 16 bits) accesses to the register with n address and the second operation (higher
16 bits) accesses to the register with n + 2 address.
5. Addresses that are not defined as registers are reserved for future expansion. If these
addresses are accessed, the operation is undefined and not guaranteed.
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