The RST instruction is a 1 byte opcode with a 3 bit imbedded operand. There are 8 different RST instructions. Each pushes the PC on the stack, and loads the PC with the operand's value times 8. (0H, 8H, 10H, 18H, etc.)Pushing the PC on the stack and loading a new value into the PC is exactly what a CALL instruction does, so the RST instruction is a 1 byte CALL instruction. The difference between RST and CALL is that CALL is a 3 byte instruction which can go anywhere in memory in one instruction.
RST 2 is one example of a one byte call instruction. It points to 0010H.
CALL, requiring 18 clock cycles.
The CALL instruction uses 18 clock cycles. 3x3 fetch, 2x3 store, 1x1 decode, 2x1 decrement.
the difference is that jump changes the eip pointer register to another memory location and continues the execution from the point it jumped. the call is like a function call in languages like C because it saves the memory location of the next instruction to the stack, so then with a ret instruction you can pop out from the stack that saved memory location to jump back again exactly after the call event.
A system call is started with some form of trap-instruction.
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The CALL InstructionOpcode OperandCALL 16-bit memory addressof a subroutineIt is a 3-byte instruction that transfers the program sequence to a subroutineSaves the content of the PC (Program Counter-16-bit register) , the address of the next instruction , on the stackDecrements the stack pointer register by 2Jumps unconditionally to the memory location specified by the 2nd and 3rd bytes.This instruction is accompanied by a RETURN instruction in the subroutine
A trap instruction is a software interrupt. It's generated by an error or by a user program when it needs the operating system to perform an operation (a system call).
IP(instruction Pointer) is a processor Register IP store the offset address of the next instruction IP can be modified by Jump & call condition IP can Increment by 1,2,3.......bytes Regard:tiger_ucet@yahoo.com
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