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Chapter 9 TRAP Routines and Subroutines

Chapter 9 TRAP Routines and Subroutines. System Calls. System Call. LC-3 TRAP Mechanism. TRAP Instruction. TRAP. RET (JMP R7). TRAP Mechanism Operation. TRAP Routines and their Assembler Names. Example: Using the TRAP Instruction. Example: Output Service Routine. TRAP_PUTS

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Chapter 9 TRAP Routines and Subroutines

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  1. Chapter 9TRAP Routines andSubroutines

  2. System Calls

  3. System Call

  4. LC-3 TRAP Mechanism

  5. TRAP Instruction

  6. TRAP

  7. RET (JMP R7)

  8. TRAP Mechanism Operation

  9. TRAP Routines and their Assembler Names

  10. Example: Using the TRAP Instruction

  11. Example: Output Service Routine TRAP_PUTS ST R0,OS_SAVE_R0 ; save R0, R1, and R7 ST R1,OS_SAVE_R1 ST R7,OS_SAVE_R7 ADD R1,R0,#0 ; move string pointer (R0) into R1 TRAP_PUTS_LOOP LDR R0,R1,#0 ; write characters in string using OUT BRz TRAP_PUTS_DONE OUT ADD R1,R1,#1 BRnzp TRAP_PUTS_LOOP TRAP_PUTS_DONE LD R0,OS_SAVE_R0 ; restore R0, R1, and R7 LD R1,OS_SAVE_R1 LD R7,OS_SAVE_R7 RET stored in table,location x22

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