Program Flow Control Group in PIC

Basics of PIC and other related articles

PERIPHERAL INTERFACE CONTROLLER (PIC)

INTRODUCTION TO PIC 16F877

To know the basic instruction sets, use the link below.

PIC PROGRAMMING INSTRUCTION SETS

ARITHMETIC AND LOGIC OPERATIONS GROUP

DATA TRANSFER GROUP

BIT OPERATION GROUP INSTRUCTIONS

1) BTFSC

BTFSC is a special type program flow instruction which control the current program flow. Normally BTFSC Test the bit in f, skip if it is zero.

Syntax: Label BTFSC f, b
Description: Test the specified bit of register f, skip the next instruction if it is zero
Operation: Skip the next instruction if f (b) = 0
Operand: 0 < f < 127 and 0 < b < 7
No. of words: 1
No. cycles: 1 or 2 depends on bit value
Flags: NIL

2) BTFSS

BTFSS also program flow control instruction. This instruction Test the bit in f, skip if it is one

Syntax: Label BTFSS f, b
Description: Test the specified bit of register f, skip the next instruction if it is one
Operation: Skip the next instruction if f (b) = 1
Operand: 0 < f < 127 and 0 < b < 7
No. of words: 1
No. cycles: 1 or 2 depends on bit value
Flags: nil

3) INCFSZ

INCFSZ is a content increment command which Increment f content, skip if it is zero

Syntax: Label INCFSZ f, d

Description: Increment the f content, skip the next instruction if f is zero
Operation: Skip the next instruction if f = zero
Operand: (f) + 1 = w if d = 0 and (f) + 1 = f if d = 1
No. of words: 1
No. cycles: 1 or 2 depends on bit value
Flags: nil

4) DECFSZ

DECFSZ command Decrement f content, skip if it is zero

Syntax: Label DECFSZ f, d
Description: Decrement the f content, skip the next instruction if f is zero
Operation: Skip the next instruction if f = zero
Operand: (f) – 1 = w if d = 0 and (f) – 1 = f if d = 1
No. of words: 1
No. cycles: 1 or 2 depends on bit value
Flags: nil

5) GOTO

GOTO instruction is used for Jump to specified address locations.

Syntax: Label GOTO Label
Description: Unconditional jump to specified label
Operation: k to PC(10:0), PCLATH(4:3) to PC(12:11)
Operand: 0 < k < 2048
No. of words: 1
No. cycles: 2
Flags: nil

6) CALL

CALL command is used for Call the required sub-program or other values.

Syntax: Label CALL Label
Description: Unconditional call the label
Operation: (PC) + 1 to Top of stack, k to PC(10:0), PCLATH(4:3) to PC(12:11)
Operand: 0 < k < 2048
No. of words: 1
No. cycles: 2
Flags: nil

7) RETURN

RETURN command is used for Return to main program from any other sub programs

Syntax: Label RETURN
Description: Unconditional return from subroutine
Operation: Top of stack to (PC)
Operand: nil
No. of words: 1
No. cycles: 2
Flags: nil

8) RETLW

RETLW is also a return command. By using this command, Return to main program with k in w reg .

Syntax: Label RETLW k
Description: Unconditional return from subroutine
Operation: Top of stack to (PC) and k loaded in w register
Operand: 0 < k < 255
No. of words: 1
No. cycles: 2
Flags: nil

9) RETFIE

RETFIE used to return from interrupt routine

Syntax: Label RETFIE
Description: Unconditional return from subroutine
Operation: Top of stack to (PC) and Global Interrupt bit is enabled
Operand: nil
No. of words: 1
No. cycles: 2
Flags: nil

Other Instructions in PIC

1) NOP

NOP command used for denoting No Operation

Syntax: Label NOP
Description: No operation
Operation: nil
Operand: nil
No. of words: 1
No. cycles: 1
Flags: nil

2) CLRWDT

CLRWDT command used for Initialize watchdog time feature .

Syntax: Label CLRWDT
Description: Watchdog timer and pre-scalar is reset and TO and PD are set
Operation: 0 to WDT, 0 to pre-scalar and Status bits TO and PD are set
Operand: TO and PD
No. of words: 1
No. cycles: 1
Flags: nil

3) SLEEP

SLEEP command used for initialize Standby mode.

Syntax: Label SLEEP
Description: Goes into low consumption, OSC is stopped, Watchdog timer and pre-scalar is reset and TO and PD bits are set
Operation: 0 to WDT, 0 to pre-scalar and Status bits, TO is set and PD is reset
Operand: TO and PD
No. of words: 1
No. cycles: 1
Flags: nil