Samsung C8278X ユーザーズマニュアル

2-13 

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.  

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).  

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. 

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.  

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.  

 

 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

Register File

Contains 32

8-Byte Slices

RP0

RP1

8H
7H

0  0  0  0  1  X  X  X

0  0  0  0  0  X  X  X

8-Byte Slice

8-Byte Slice