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.
A two-byte instruction gives the specific function instruction in two bytes, or two words. The first specifies the opcode, which tells the microprocessor what operation will occur. The second specifies the operand, or the data that the operation is done on.
32 byte
In 8086 the instruction queue is 6 byte long. This is because even the longest 8086 instruction is 6 byte long. Thus it is possible to prefetch even the longest instruction in the instruction set.
32 byte
16 bits is a byte, for the record half a byte is called a "nibble". I kid you not...
1byte instruction = MOV A,B 2byte instruction = MVI A,01H 3byte instruction = STA 2030H
It depends on whether the machine code is one, two, or three bytes long, and on whether or not the instruction transferred control to another location. In the case of a non-jump single byte instruction, the PC will have a value of 2060H after the instruction is complete, and it will be 2061H or 2062H after a two or three byte instruction. In the case of a jump, call, or interrupt, the PC will depend on the instruction.
There are 74 instructions in the 8085 microprocessor.
when this interrupt occurs, the processor fetches the bus one instruction usually one of these instructions as given, one of the 8 RST instructions( RST0 - RST7), the processor saves the current program counter into the stack and the branches from N*8 (where N is 3 bit number from 0 to 7). call instruction which is a 3 byte inst. the first byte is the address branch which chosen based on the second and the third byte of the instruction set.
SIM stands for “Set Interrupt Mask” It is 1 byte instruction RIM stands for “Read Interrupt Mask” it is 1 byte MULTI-PURPOSE instruction.
SJMP is short jump. In this 2-byte instruction the first byte is opcode and second byte is relative address of target location. This can save some byte of memory in many applications where memory space is in short supply where as LJMP (Long Jump) is 3-byte instruction in which 1st byte is opcode and 2nd and 3rd byte represent the 16- bit address of target location.