Register Addressing - Samsung S3F84B8 User Manual

S3F84B8_UM_REV 1.00 2 ADDRESS SPACES

2.4 REGISTER ADDRESSING

The S3C8 series register architecture provides an efficient method of working register addressing and takes full
advantage of shorter instruction formats to reduce the execution time.
In Register (R) addressing mode, the operand value specifies the content of a specific register or register pair.
Here, you can access any location in the register file, except for set 2. With working register addressing, you can
use a register pointer to specify an 8 byte working register space in the register file and an 8-bit register within that
space.
Registers are addressed either as a single 8-bit register or a paired 16-bit register space. In a 16-bit register pair,
the address of first 8-bit register is always an even number and the address of next register is always an odd
number. The most significant byte (MSB) of 16-bit data is always stored in the even-numbered register, and the
least significant byte (LSB) is always stored in the next (+1) odd-numbered register.
Working register addressing differs from Register addressing, since it uses a register pointer to identify a specific
8 byte working register space in the internal register file and a specific 8-bit register within that space.
MSB LSB n = Even address
Rn Rn+1
Figure 2-9 16-Bit Register Pair
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