Filter
Top Products
ADDRESS SPACES S3C8275X/F8275X/C8278X/F8278X/C8274X/F8274X
2-12
WORKING REGISTERS
Instructions can access specific 8-bit registers or 16-bit register pairs using either 4-bit or 8-bit address fields.
When 4-bit working register addressing is used, the 256-byte register file can be seen by the programmer as one
that consists of 32 8-byte register groups or "slices." Each slice comprises of eight 8-bit registers.
Using the two 8-bit register pointers, RP1 and RP0, two working register slices can be selected at any one time to
form a 16-byte working register block. Using the register pointers, you can move this 16-byte register block
anywhere in the addressable register file, except the set 2 area.
The terms slice and block are used in this manual to help you visualize the size and relative locations of selected
working register spaces:
— One working register slice is 8 bytes (eight 8-bit working registers, R0–R7 or R8–R15)
— One working register block is 16 bytes (sixteen 8-bit working registers, R0–R15)
All the registers in an 8-byte working register slice have the same binary value for their five most significant
address bits. This makes it possible for each register pointer to point to one of the 24 slices in the register file.
The base addresses for the two selected 8-byte register slices are contained in register pointers RP0 and RP1.
After a reset, RP0 and RP1 always point to the 16-byte common area in set 1 (C0H–CFH).
Each register pointer points to
one 8-byte slice of the register
space, selecting a total 16-byte
working register block.
1 1 1 1 1 X X X
RP1 (Registers R8-R15)
RP0 (Registers R0-R7)
Slice 32
Slice 31
~ ~
CFH
C0H
FFH
F8H
F7H
F0H
FH
8H
7H
0H
Slice 2
Slice 1
10H
Set 1
Only
0 0 0 0 0 X X X
Figure 2-7. 8-Byte Working Register Areas (Slices)