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ADDRESS SPACES S3C8245/P8245/C8249/P8249
2-6
REGISTER SET 1
The term set 1 refers to the upper 64 bytes of the register file, locations C0H–FFH.
The upper 32-byte area of this 64-byte space (E0H–FFH) is expanded two 32-byte register banks, bank 0 and bank
1. The set register bank instructions, SB0 or SB1, are used to address one bank or the other. A hardware reset
operation always selects bank 0 addressing.
The upper two 32-byte areas (bank 0 and bank 1) of set 1 (E0H–FFH) contains 50 mapped system and peripheral
control registers. The lower 32-byte area contains 16 system registers (D0H–DFH) and a 16-byte common working
register area (C0H–CFH). You can use the common working register area as a “scratch” area for data operations
being performed in other areas of the register file.
Registers in set 1 locations are directly accessible at all times using Register addressing mode. The 16-byte
working register area can only be accessed using working register addressing (For more information about working
register addressing, please refer to Chapter 3, “Addressing Modes.”)
REGISTER SET 2
The same 64-byte physical space that is used for set 1 locations C0H–FFH is logically duplicated to add another 64
bytes of register space. This expanded area of the register file is called set 2. For the S3C8249,
the set 2 address range (C0H–FFH) is accessible on pages 0–3.
S3C8245, the set 2 address range (C0H-FFH) is accessible on pages 0-1.
The logical division of set 1 and set 2 is maintained by means of addressing mode restrictions. You can use only
Register addressing mode to access set 1 locations. In order to access registers in set 2, you must use Register
Indirect addressing mode or Indexed addressing mode.
The set 2 register area is commonly used for stack operations.