Samsung F8278X 用户手册
S3C8275X/F8275X/C8278X/F8278X/C8274X/F8274X
ADDRESS
SPACES
2-13
USING THE REGISTER POINTS
Register pointers RP0 and RP1, mapped to addresses D6H and D7H in set 1, are used to select two movable
8-byte working register slices in the register file. After a reset, they point to the working register common area:
RP0 points to addresses C0H–C7H, and RP1 points to addresses C8H–CFH.
8-byte working register slices in the register file. After a reset, they point to the working register common area:
RP0 points to addresses C0H–C7H, and RP1 points to addresses C8H–CFH.
To change a register pointer value, you load a new value to RP0 and/or RP1 using an SRP or LD instruction.
(see Figures 2-8 and 2-9).
(see Figures 2-8 and 2-9).
With working register addressing, you can only access those two 8-bit slices of the register file that are currently
pointed to by RP0 and RP1. You cannot, however, use the register pointers to select a working register space in
set 2, C0H–FFH, because these locations can be accessed only using the Indirect Register or Indexed
addressing modes.
pointed to by RP0 and RP1. You cannot, however, use the register pointers to select a working register space in
set 2, C0H–FFH, because these locations can be accessed only using the Indirect Register or Indexed
addressing modes.
The selected 16-byte working register block usually consists of two contiguous 8-byte slices. As a general
programming guideline, it is recommended that RP0 point to the "lower" slice and RP1 point to the "upper" slice
(see Figure 2-8). In some cases, it may be necessary to define working register areas in different (non-
contiguous) areas of the register file. In Figure 2-9, RP0 points to the "upper" slice and RP1 to the "lower" slice.
programming guideline, it is recommended that RP0 point to the "lower" slice and RP1 point to the "upper" slice
(see Figure 2-8). In some cases, it may be necessary to define working register areas in different (non-
contiguous) areas of the register file. In Figure 2-9, RP0 points to the "upper" slice and RP1 to the "lower" slice.
Because a register pointer can point to either of the two 8-byte slices in the working register block, you can
flexibly define the working register area to support program requirements.
flexibly define the working register area to support program requirements.
PROGRAMMING TIP — Setting the Register Pointers
SRP
#70H
;
RP0
← 70H, RP1 ← 78H
SRP1
#48H
;
RP0
← no change, RP1 ← 48H,
SRP0
#0A0H
;
RP0
← A0H, RP1 ← no change
CLR
RP0
;
RP0
← 00H, RP1 ← no change
LD
RP1,#0F8H ;
RP0
← no change, RP1 ← 0F8H
FH (R15)
0H (R0)
16-Byte
Contiguous
Working
Register block
Contiguous
Working
Register block
Register File
Contains 32
8-Byte Slices
RP0
RP1
8H
7H
7H
0 0 0 0 1 X X X
0 0 0 0 0 X X X
8-Byte Slice
8-Byte Slice
Figure 2-8. Contiguous 16-Byte Working Register Block