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ADDRESS SPACES S3C8245/P8245/C8249/P8249
2-10
16-Byte
Contiguous
working
Register block
Register File
Contains 32
8-Byte Slices
0 0 0 0 0 X X X
RP1
1 1 1 1 0 X X X
RP0
0H (R0)
7H (R15)
F0H (R0)
F7H (R7)
8-Byte Slice
8-Byte Slice
Figure 2-7. Non-Contiguous 16-Byte Working Register Block
+ PROGRAMMING TIP — Using the RPs to Calculate the Sum of a Series of Registers
Calculate the sum of registers 80H–85H using the register pointer. The register addresses from 80H through 85H
contain the values 10H, 11H, 12H, 13H, 14H, and 15 H, respectively:
SRP0 #80H ; RP0 ← 80H
ADD R0,R1 ; R0 ← R0 + R1
ADC R0,R2 ; R0 ← R0 + R2 + C
ADC R0,R3 ; R0 ← R0 + R3 + C
ADC R0,R4 ; R0 ← R0 + R4 + C
ADC R0,R5 ; R0 ← R0 + R5 + C
The sum of these six registers, 6FH, is located in the register R0 (80H). The instruction string used in this example
takes 12 bytes of instruction code and its execution time is 36 cycles. If the register pointer is not used to calculate
the sum of these registers, the following instruction sequence would have to be used:
ADD 80H,81H ; 80H ← (80H) + (81H)
ADC 80H,82H ; 80H ← (80H) + (82H) + C
ADC 80H,83H ; 80H ← (80H) + (83H) + C
ADC 80H,84H ; 80H ← (80H) + (84H) + C
ADC 80H,85H ; 80H ← (80H) + (85H) + C
Now, the sum of the six registers is also located in register 80H. However, this instruction string takes 15 bytes of
instruction code rather than 12 bytes, and its execution time is 50 cycles rather than 36 cycles.