s3c72m9 Samsung Semiconductor, Inc., s3c72m9 Datasheet - Page 21

• Manufacturer Part Number: s3c72m9
• Description: The S3c72m5/s3c72m7/s3c72m9 Single-chip Cmos Microcontroller Has Been Designed For High Performance Using Samsung S
• Manufacturer: Samsung Semiconductor, Inc.

S3C72M5/C72M7/C72M9/P72M9 (Preliminary Spec)
ADDRESS SPACES
INSTRUCTION REFERENCE AREA
Using 1-byte REF instructions, you can easily reference instructions with larger byte sizes that are stored in ad-
dresses 0020H–007FH of program memory. This 96-byte area is called the REF instruction reference area, or look-
up table. Locations in the REF look-up table may contain two one-byte instructions, a single two-byte instruction, or
three-byte instruction such as a JP (jump) or CALL. The starting address of the instruction you are referencing must
always be an even number. To reference a JP or CALL instruction, it must be written to the reference area in a two-
byte format: for JP, this format is TJP; for CALL, it is TCALL. In summary, there are three ways to the REF
instruction:
By using REF instructions to execute instructions larger than one byte, you can improve program execution time
considerably by reducing the number of program steps. In summary, there are three ways you can use the REF
instruction:
— Using the 1-byte REF instruction to execute one 2-byte or two 1-byte instructions,
— Branching to any location by referencing a branch instruction stored in the look-up table,
— Calling subroutines at any location by referencing a call instruction stored in the look-up table.
2-5