What is trap x25?
TRAP x25. HALT: halt the program. TRAP x24. PUTSP: records input strings, each register holds a pair of characters, address of first character stored in r0.
What is the trap vector table LC-3?
Memory locations x0000 through x00FF, 256 in all, are available to contain starting addresses for system calls specified by their corresponding trap vectors. This region of memory is called the Trap Vector Table.
What does trap instruction do?
A trap instruction is a procedure call that synchronously transfers the control. It is a software interrupt generated by the user program or by an error when the operating system is needed by it to perform the system calls or an operation.
What is the trap vector table?
• trapvect8 is an 8-bit offset. – Used to determine the starting address of a TRAP routine. – Trap vector table is in memory locations x0000 through x00FF and contains. starting addresses of the TRAP routines.
What is halt LC-3?
HALT tells the simulator to stop a program that is running. .
How many traps can the LC-3 support?
256 trap routines can be implemented in the LC-3. Why must a RET instruction be used to return from a TRAP routine?
What is halt lc3?
What does a CPU do when a trap occurs?
When an interrupt or trap occurs, the CPU stores the program counter in the trap program counter register TPC. If the trap occurred because of a memory addressing fault, the memory address and a notice of the cause is stored in the trap memory address register TMA.
What is halt LC3?
What is LD in LC3?
LD (LoaD) LDI (LoaD Indirect)
What is sext in LC-3?
SEXT(immediate): sign-extend immediate to 16 bits. ZEXT(immediate): zero-extend immediate to 16 bits. Page 2 has an ASCII character table.
Where are the instructions stored in the LC3 trap?
The first instruction of the trap routine is stored at the address specified in the TRAP instruction, rather than the starting address of the trap routine. In his new design, he still wants to implement as many TRAP routines as the original LC-3 TRAP.
How are an interrupt and a trap similar?
the TRAP service routine. TRAP & Interrupts – Similar mechanisms – A TRAP is an instruction (event internal to a program). – An interrupt is external to a program (from an I/O device) – Both invoke a supervisor service routine.
How many lines does a trap subroutine need?
A Trap subroutine is as large as it needs to be to execute a particular function. But if you’re only counting the required lines needed in a subroutine then you would need at least 7 (or 1 if you only wanted your routine to return to the command that called it).
Is your class using the Mc Graw Hill LC-3 simulator?
Is your class using the Mc Graw Hill LC-3 Simulator? Because reading through their text on the TRAP command, bits [8:11] aren’t even sent to the MAR to load from memory, they’re just dropped. Only bits [7:0] are used because they point to a location in the Trap Vector Table.
