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The general syntax for each line of the assembly file is:
[label] [command|instruction][parameter [,parameter...]] [comment]
Example lines for assembly:
main GOTO subroutine - An address label (main) and machine instruction (GOTO)my_label EQU 12- A label (my_label) and assembler command (EQU)
;This is a comment- A comment, ignored by the assembler
Instruction Set
This is not meant as an introduction to the PIC® MCU family, as there are
much better written texts on the subject. However, in version 2.0
the assembler will recognise the standard Microchip mnemonics for 12-
and 14-bit microcontrollers. These are detailed below. The instructions shown with a
grey background are only available for 14-bit devices.
Instruction Meaning Status 14-bit Opcode 12-bit Opcode NOP No operation None 00 0000 0000 0000 0000 0000 0000 CLRF f Clear f Z 00 0001 1fff ffff 0000 011f ffff CLRW Clear W Z 00 0001 0000 0011 0000 0100 0000 MOVLW v Move Literal to W None 11 00xx vvvv vvvv 1100 vvvv vvvv MOVWF f Move W to f None 00 0000 1fff ffff 0000 001f ffff MOVF f,d Move f Z 00 1000 dfff ffff 0010 00df ffff SWAPF f,d Swap halves f None 00 1110 dfff ffff 0011 10df ffff COMF f,d Complement f Z 00 1001 dfff ffff 0010 01df ffff Mathematic Instructions
ADDLW v Add literal to W C,DC,Z 11 111x vvvv vvvv - n/a -
SUBLW v Subtract W from literal C,DC,Z 11 110x vvvv vvvv - n/a - ANDLW v AND literal and W Z 11 1001 vvvv vvvv 1110 vvvv vvvv IORLW v Incl. OR literal and W Z 11 1000 vvvv vvvv 1101 vvvv vvvv XORLW v Exclusive OR literal and W Z 11 1010 vvvv vvvv 1111 vvvv vvvv ADDWF f,d Add W and f C,DC,Z 00 0111 dfff ffff 0001 11df ffff SUBWF f,d Subtract W from f C,DC,Z 00 0010 dfff ffff 0000 10df ffff ANDWF f,d AND W and f Z 00 0101 dfff ffff 0001 01df ffff IORWF f,d Inclusive OR W and f Z 00 0100 dfff ffff 0001 00df ffff XORWF f,d Exclusive OR W and f Z 00 0110 dfff ffff 0001 10df ffff DECF f,d Decrement f Z 00 0011 dfff ffff 0000 11df ffff DECFSZ f,d Decrement f, skip if zero None 00 1011 dfff ffff 0010 11df ffff INCF f,d Increment f Z 00 1010 dfff ffff 0010 10df ffff INCFSZ f,d Increment f, skip if zero None 00 1111 dfff ffff 0011 11df ffff RLF f,d Rotate left f C 00 1101 dfff ffff 0011 01df ffff RRF f,d Rotate right f C 00 1100 dfff ffff 0011 00df ffff Control Instructions CALL k Call subroutine at k None 10 0kkk kkkk kkkk 1001 kkkk kkkk GOTO k Goto address k None 10 1kkk kkkk kkkk 101k kkkk kkkk
RETURN Return from subroutine None 00 0000 0000 1000 - n/a -
RETFIE Return from Interrupt None 00 0000 0000 1001 - n/a - RETLW v Return with literal in W None 11 01xx vvvv vvvv 1000 vvvv vvvv Bit Instructions BCF f,b Bit clear f None 01 00bb bfff ffff 0100 bbbf ffff BSF f,b Bit set f None 01 01bb bfff ffff 0101 bbbf ffff BTFSC f,b Bit test, skip if clear None 01 10bb bfff ffff 0110 bbbf ffff BTFSS f,b Bit test, skip if set None 01 11bb bfff ffff 0111 bbbf ffff Special Instructions SLEEP Processor Sleep TO,PD 00 0000 0110 0011 0000 0000 0011 CLRWDT Clear Watchdog timer TO,PD 00 0000 0110 0100 0000 0000 0100
OPTION Load OPTION register None - n/a - 0000 0000 0010 TRIS f Tristate port f None 00 0000 0110 0fff 0000 0000 0fff
Key:
In addition to these core instructions, the standard Microchip assembler supports a number of 'Alias' instructions which are short forms of those above. Some alias instructions encode to a specific single opcode. Others may encode to two separate processor instructions. The alias instructions are listed below:
Instruction Parameters Meaning Equivalent ADDCF f,d Add Carry to Register BTFSC 3,0
INCF f,d ADDDCF f,d Add Digit Carry to Register BTFSC f,d
INCF 3,1 B k Branch GOTO k BC k Branch on Carry BTFSC 3,0
GOTO k BDC k Branch on Digit Carry BTFSC 3,1
GOTO k BNC k Branch on No Carry BTFSS 3,0
GOTO k BNDC k Branch on No Digit Carry BTFSS 3,1
GOTO k BNZ k Branch on No Zero BTFSS 3,2
GOTO k BZ k Branch on Zero BTFSC 3,2
GOTO k CLRC Clear Carry BCF 3,0 CLRDC Clear Digit Carry BCF 3,1 CLRZ Clear Zero BCF 3,2 MOVFW f Move Register to W MOVF f,0 NEGF f,d Negate Register COMF f,1
INCF f,d SETC Set Carry BSF 3,0 SETDC Set Digit Carry BSF 3,1 SETZ Set Zero BSF 3,2 SKPC Skip on Carry BTFSS 3,0 SKPDC Skip on Digit Carry BTFSS 3,1 SKPNC Skip on No Carry BTFSC 3,0 SKPNDC Skip on No Digit Carry BTFSC 3,1 SKPNZ Skip on Non Zero BTFSC 3,2 SKPZ Skip on Zero BTFSS 3,2 SUBCF f,d Subtract Carry from Register BTFSC 3,0
DECF f,d SUBDCF f,d Subtract Digit Carry from Register BTFSC 3,1
DECF f,d TSTF f Test Register MOVF f,1
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