actually register holds the data..there are 6 register which are temporary registers..program counter holds the address of next instruction to be fetched..instruction register holds the currently executed data...
add B
If 8 or 16 bit data is required for executing the instruction present in register/register pair and named of register/register pair is given along the register.this instruction is called register addressing mode instruction.for example:MOV B,A
It is used to hold data or the memory address that contains either the next place of data or an instruction that is to be used .
The instruction opcode is a type of data contained in memory, pointed to by the PC (Program Counter) register.
Block diagram of the von Neumann architecture: MQ, multiplier quotient register; IR, instruction register; IBR, instruction buffer register; MAR, memory address register; MDR, memory data register
instruction register
Every instruction contains to parts: operation code[opcode],and operand. The first part of an instruction which specifies the task to be performed by the computer is called opcode. The second part of the instruction is the data to be operated on.,and it is called operand. The operand[or data]given in the instruction may be in various forms such as 8-bit or 16-bit data, 8-bit or 16-bit address, internal register or a register or memory location.
In the 8085 microprocessor, the MOV instruction copies data between two registers, or between a register and memory. The MVI instruction differs only in that the source data is contained in the byte immediately following the opcode byte.
The MAR is a special register in the sense that each time it is accessed from the outside, memory senses it and considers the new content of the MAR an address.
Instruction register:- it hold's the instruction decoded bu control unit.. if you know that bus is the communication Chanel of computer system, whenever we enter some instruction it's going to pass by bus. but we send instruction in human understandable form so all data should be convert in bus understandable form. now all data convert in bus understandable form but here is the problem that what C.P.U. not able to understand that , so control unit convert all instruction in c.p.u. understandable form now all data converted in c.p.u. understandable form but still there in c.p.u. going some process so it can accept that thing right now ..so it can store in some where in c.p.u. that called instruction register.. I.R is the one type of register.it can hold very small amount of data.
It is register addressing mode, as it moves the content of HL to PC which is data and not address.