Department of Computer Scien

ce and Information Engineering

National Cheng Kung University, TAIWAN

CALL HANEL

INSTRUCTIONS

‰Call instruction is used to call subroutine

¾Subroutines are often used to perform tasks that need to be performed frequently¾This makes a program more structured in addition to saving memory space

LCALL

(long call)¾3-byte instructionƒFirst byte is the opcodeƒSecond and third bytes are used for address of target subroutine

• Subroutine is located anywhere within 64K byte address space
  ACALL

(absolute call)¾2-byte instructionƒ11 bits are used for addr

ess within 2K-byte range