
CHAPTER 3 CPU FUNCTIONS
User’s Manual U12768EJ4V1UD
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(3) On-chip peripheral I/O area
A 4 KB area of addresses FFF000H to FFFFFFH is reserved as an on-chip peripheral I/O area.
The V850/SA1 is provided with a 1 KB area of addresses FFF000H to FFF3FFH as a physical on-chip 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 operation mode specification and state monitoring for the on-chip
peripherals are all memory-mapped to the on-chip peripheral I/O area. Program fetches are not allowed in this
area.
Figure 3-12. On-Chip Peripheral I/O Area
xxFFFFFFH
xxFFFC00H
xxFFFBFFH
xxFFF800H
xxFFF7FFH
xxFFF400H
xxFFF3FFH
xxFFF000H
Image
Physical on-chip
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 at 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 halfword 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 at address n that can be accessed only in halfword units is accessed in word
units, the operation is replaced with two halfword operations. The first operation (lower 16
bits) accesses the register at address n and the second operation (higher 16 bits)
accesses the register at address n + 2.
4. If a register at address n that can be accessed in word units is accessed with a word
operation, the operation is replaced with two halfword operations.
The first operation
(lower 16 bits) accesses the register at address n and the second operation (higher 16 bits)
accesses the register at address n + 2.
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.