SECTION III-1: MOVWF Instruction in the PIC micro-controller

The PIC allows direct access to other locations in the file register for ALU and other operations. In this section we show the instructions using various locations of the file register.

MOVWF Instruction:-

The access bank of the file register is the default bank upon powering up the PIC18. The term file register must be emphasized because the instructions have the letter F in their mnemonics. In instructions such as MOVWF, the F stands for a location in the file register, while W means WREG. The MOVWF instruction tells the CPU to move, in reality copy, the source register of WREG to a destination in the file register (F). After this instruction is executed, the location in the file register will have the same value as register WREG. The location in the file register can be one of the special function registers SFRs or a location in the general purpose register region. For example: The "MOVWF PORTA" instruction will move the contents of WREG into the SFR register called PORTA.

The following program first loads the WREG register with value 55H, then moves this value around to various SFRs of PORT B, C and D.

PORTB, PORTC, and PORTD are part of the special function registers in the file register as shown in figure below. They can be connected to the I / O pins of the PIC micro-controller.

Special Function Registers of the PIC18 Family

We can also move (copy) the contents of WREG into any location in the general purpose registers (RAM) region of the file registers. The following program will put 99H into locations 0 - 4 of the general purpose register GPR region in the file register:

The chart indicates the contents of addresses 0 - 4 after execution of the code

As shown in the chart below: