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Data Transfer Group Instructions in PIC

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PERIPHERAL INTERFACE CONTROLLER (PIC)

PIC PROGRAMMING – INSTRUCTION SETS

INTRODUCTION TO PIC 16F877

Data Transfer Group Instructions in PIC

Data transfer group instructions are one of the major instructions widely used in PIC programming for data transfer purposes. By using these types of instructions, we can move or change the value (bits) from one location to another.

Data Transfer Instructions with Syntaxes

1. MOVLW

“MOVLW” instruction is used to write constant in W register (move the value from literal to W register).

Syntax:

Label MOVLW k

Description:

8 bit constant is written in W reg.

Operation:

k to (W)

Operand:

0 < k < 255

No. of words: 1 No. cycles: 1 Flags: Nil 2. MOVWF

MOVWF instruction is used to move the data (bits) from W register to flag register F (copy/move the value from W register to F register).

Syntax:

Label MOVWF f

Description:

Content of W is copied into f register (flag register).

Operation:

W to (f) (W register to Flag register)

Operand:

0 < f < 127

No. of words: 1 No. cycles: 1 Flags: Nil 3. MOVF

MOVF command is used for copy/move the contents (bits) in the flag register to D register (Copy f to d register).

D register (destination register) is a special register which can be switchable in its destination according to its status. If the status of D register is ‘0’, the destination is W register and if the status is ‘1’, the destination of D register became F register (flag)

Syntax:

Label MOVF f, d

Description:

Content of f is copied into destination.

If d = 0, the destination is W register

If d = 1, the destination is f register

Operation:

F to (D)

Operand:

0 < k < 127

No. of words: 1 No. cycles: 1 Flags: Z 4. CLRW

CLRW is a clearing instruction that helps to reset the values of W register to ‘0’ (write ‘0’ in W register).

Syntax:

Label CLRW

Description:

Zero is copied into W register

Z flag in status register is set to one

Operation:

0 to (W)

Operand: nil No. of words: 1 No. cycles: 1 Flags: Z 5. CLRF f

CLRF f Write ‘0’ in F register that helps to reset the current status to ‘0’

Syntax:

Label CLRF f

Description:

Zero is copied into f register

Z flag in status register is set to one

Operation:

0 to (f)

Operand: nil No. of words: 1 No. cycles: 1 Flags: Z 6. SWAPF

SWAPF used for swap (interchanging functions) functions which Swap the nibbles (4bits).The destination of this function depends on the destination register status.

Syntax:

Label SWAPF f, d

Description:

Upper, Lower nibbles are exchanged

If d = 0, the destination is W register

If d = 1, the destination is f register

Operation:

f (0:3) to d(4:7) and f(4:7) to d(0:3)

Operand:

0 < f < 127

No. of words: 1 No. cycles: 1 Flags: —