42.1 Standard Instruction Set

The standard PIC18 instruction set adds many enhancements to the previous PIC^® MCU instruction sets while maintaining an easy migration from these PIC MCU instruction sets. Most instructions are a single program memory word (16 bits), but there are a few instructions that require two- or three-program memory locations.

Each single-word instruction is a 16-bit word divided into an opcode that specifies the instruction type and one or more operands, which further specifies the operation of the instruction.

The instruction set is highly orthogonal and is grouped into four basic categories:

Byte-oriented operations
Bit-oriented operations
Literal operations
Control operations

The PIC18 instruction set summary in Table 42-2 lists byte-oriented, bit-oriented, literal and control operations. Table 42-1 shows the opcode field descriptions.

Most byte-oriented instructions have three operands:

The file register (specified by ‘f’)
The destination of the result (specified by ‘d’)
The accessed memory (specified by ‘a’)

The file register designator ‘f’ specifies which file register is to be used by the instruction. The destination designator ‘d’ specifies where the result of the operation is to be placed. If ‘d’ is zero, the result is placed in the WREG register. If ‘d’ is one, the result is placed in the file register specified in the instruction.

All bit-oriented instructions have three operands:

The file register (specified by ‘f’)
The bit in the file register (specified by ‘b’)
The accessed memory (specified by ‘a’)

The bit field designator ‘b’ selects the number of the bit affected by the operation, while the file register designator ‘f’ represents the number of the file in which the bit is located.

The literal instructions may use some of the following operands:

A literal value to be loaded into a file register (specified by ‘k’)
The desired FSR register to load the literal value into (specified by ‘f’)
No operand required (specified by ‘—’)

The control instructions may use some of the following operands:

A program memory address (specified by ‘n’)
The mode of the CALL or RETURN instructions (specified by ‘s’)
The mode of the table read and table write instructions (specified by ‘m’)
No operand required (specified by ‘—’)

All instructions are a single word, except for a few two- or three-word instructions. These instructions were made two- or three-words to contain the required information in 32 or 48 bits. In the second and third words, the four MSbs are ‘1’s. If this second or third word is executed as an instruction (by itself), it will execute as a NOP.

All single-word instructions are executed in a single instruction cycle, unless a conditional test is true or the Program Counter is changed as a result of the instruction. In these cases, the execution takes two instruction cycles, with the additional instruction cycle(s) executed as a NOP.

The two-word instructions execute in two instruction cycles and three-word instructions execute in three instruction cycles.

One instruction cycle consists of four oscillator periods. Thus, for an oscillator frequency of 4 MHz, the normal instruction execution time is 1 μs. If a conditional test is true or the Program Counter is changed as a result of an instruction, the instruction execution time is 2 μs. Two-word branch instructions (if true) take 3 μs.

Figure 42-1, Figure 42-2 and Figure 42-3 show the general formats that the instructions can have. All examples use the convention ‘nnh’ to represent a hexadecimal number.

The Instruction Set Summary, shown in Table 42-2, lists the standard instructions recognized by the Microchip MPASM^TM Assembler.

The Standard Instruction Set section provides a description of each instruction.

Table 42-1. Opcode Field Descriptions
Field	Description
`a`	RAM access bit a = `0`: RAM location in Access RAM (BSR register is ignored) a = `1`: RAM bank is specified by BSR register (default)
`ACCESS`	ACCESS = `0`: RAM access bit symbol
`BANKED`	BANKED = `1`: RAM access bit symbol
`bbb`	Bit address within an 8-bit file register (0 to 7)
`BSR`	Bank Select Register (BSR). Used to select the current RAM bank.
`d`	Destination select bit d = `0`: store result in WREG d = `1`: store result in file register f (default)
`dest`	Destination: either the WREG register or the specified register file location
`f`	8-bit register file address (`00h` to `FFh`)
`f_n`	FSR Number (0 to 2)
`f_s`	12-bit register file address (`000h` to `FFFh`) or 14-bit register file address (`0000h` to `3FFFh`). This is the source address.
`f_d`	12-bit register file address (`000h` to `FFFh`) or 14-bit register file address (`0000h` to `3FFFh`). This is the destination address.
`z_s`	7-bit literal offset for FSR2 to used as register file address (`000h` to `FFFh`). This is the source address.
`z_d`	7-bit literal offset for FSR2 to used as register file address (`000h` to `FFFh`). This is the destination address.
`k`	Literal field, constant data or label (may be either a 6-bit, 8-bit, 12-bit or a 20-bit value)
`label`	Label name
`mm` `` `+` `-` `+`	The mode of the TBLPTR register for the table read and table write instructions. Only used with table read and table write instructions: No change to register (such as TBLPTR with table reads and writes) Post-Increment register (such as TBLPTR with table reads and writes) Post-Decrement register (such as TBLPTR with table reads and writes) Pre-Increment register (such as TBLPTR with table reads and writes)
`n`	The relative address (two’s complement number) for relative branch instructions or the direct address for call/branch and return instructions
`PRODH`	Product of multiply high byte
`PRODL`	Product of multiply low byte
`s`	Fast Call/Return mode select bit s = `0`: do not update into/from shadow registers (default) s = `1`: certain registers loaded into/from shadow registers (Fast mode)
`u`	Unused or unchanged
`W`	W = `0`: Destination select bit symbol
`WREG`	Working register (accumulator)
`x`	Don’t care (‘`0`’ or ‘`1`’). The assembler will generate code with x = `0`. It is the recommended form of use for compatibility with all Microchip software tools.
`TBLPTR`	21-bit Table Pointer (points to a program memory location)
`TABLAT`	8-bit table latch
`TOS`	Top-of-stack (TOS)
`PC`	Program Counter
`PCL`	Program Counter low byte
`PCH`	Program Counter high byte
`PCLATH`	Program Counter high byte latch
`PCLATU`	Program Counter upper byte Latch
`GIE`	Global Interrupt Enable bit
`WDT`	Watchdog Timer
`TO`	Time-Out bit
`PD`	Power-Down bit
`C, DC, Z, OV, N`	ALU Status bits: Carry, Digit Carry, Zero, Overflow, Negative
`{ }`	Optional argument
`[ ]`	Indexed address
`( )`	Contents
`< >`	Register bit field
`[expr]<n>`	Specifies bit `n` of the register indicated by pointer `expr`
`→`	Assigned to
`∈`	In the set of
`italics`	User defined term (font is Courier)

Figure 42-1. General Format for Byte-Oriented Instructions

Figure 42-2. General Format for Bit-Oriented and Literal Instructions

Figure 42-3. General Format for Control Instructions

Table 42-2. Standard Instruction Set
Mnemonic, Operands		Description	Cycles	16-Bit Instruction Word				Status Affected	Notes
Mnemonic, Operands		Description	Cycles	MSb			LSb	Status Affected	Notes
BYTE-ORIENTED FILE REGISTER INSTRUCTIONS
ADDWF	f, d, a	Add WREG and f	1	`0010`	`01da`	`ffff`	`ffff`	C, DC, Z, OV, N	1
ADDWFC	f, d, a	Add WREG and Carry bit to f	1	`0010`	`00da`	`ffff`	`ffff`	C, DC, Z, OV, N	1
ANDWF	f, d, a	AND WREG with f	1	`0001`	`01da`	`ffff`	`ffff`	Z, N	1
CLRF	f, a	Clear f	1	`0110`	`101a`	`ffff`	`ffff`	Z
COMF	f, d, a	Complement f	1	`0001`	`11da`	`ffff`	`ffff`	Z, N	1
DECF	f, d, a	Decrement f	1	`0000`	`01da`	`ffff`	`ffff`	C, DC, Z, OV, N	1
INCF	f, d, a	Increment f	1	`0010`	`10da`	`ffff`	`ffff`	C, DC, Z, OV, N	1
IORWF	f, d, a	Inclusive OR WREG with f	1	`0001`	`00da`	`ffff`	`ffff`	Z, N	1
MOVF	f, d, a	Move f to WREG or f	1	`0101`	`00da`	`ffff`	`ffff`	Z, N	1
MOVFF	f_s, f_d	Move f_s (12-bit source) to f_d (12-bit destination)	2	`1100`	`f_sf_sf_sf_s`	`f_sf_sf_sf_s`	`f_sf_sf_sf_s`	None	1, 3, 4
MOVFF	f_s, f_d	Move f_s (12-bit source) to f_d (12-bit destination)	2	`1111`	`f_df_df_df_d`	`f_df_df_df_d`	`f_df_df_df_d`	None	1, 3, 4
MOVFFL	f_s, f_d	Move f_s (14-bit source) to f_d (14-bit destination)	3	`0000`	`0000`	`0110`	`f_sf_sf_sf_s`	None	1, 3
				`1111`	`f_sf_sf_sf_s`	`f_sf_sf_sf_s`	`f_sf_sf_df_d`
				`1111`	`f_df_df_df_d`	`f_df_df_df_d`	`f_df_df_df_d`
MOVWF	f, a	Move WREG to f	1	`0110`	`111a`	`ffff`	`ffff`	None
MULWF	f, a	Multiply WREG with f	1	`0000`	`001a`	`ffff`	`ffff`	None	1
NEGF	f, a	Negate f	1	`0110`	`110a`	`ffff`	`ffff`	C, DC, Z, OV, N	1
RLCF	f, d, a	Rotate Left f through Carry	1	`0011`	`01da`	`ffff`	`ffff`	C, Z, N	1
RLNCF	f, d, a	Rotate Left f (No Carry)	1	`0100`	`01da`	`ffff`	`ffff`	Z, N	1
RRCF	f, d, a	Rotate Right f through Carry	1	`0011`	`00da`	`ffff`	`ffff`	C, Z, N	1
RRNCF	f, d, a	Rotate Right f (No Carry)	1	`0100`	`00da`	`ffff`	`ffff`	Z, N	1
SETF	f, a	Set f	1	`0110`	`100a`	`ffff`	`ffff`	None
SUBFWB	f, d, a	Subtract f from WREG with  Borrow	1	`0101`	`01da`	`ffff`	`ffff`	C, DC, Z, OV, N	1
SUBWF	f, d, a	Subtract WREG from f	1	`0101`	`11da`	`ffff`	`ffff`	C, DC, Z, OV, N	1
SUBWFB	f, d, a	Subtract WREG from f with Borrow	1	`0101`	`10da`	`ffff`	`ffff`	C, DC, Z, OV, N	1
SWAPF	f, d, a	Swap nibbles in f	1	`0011`	`10da`	`ffff`	`ffff`	None	1
XORWF	f, d, a	Exclusive OR WREG with f	1	`0001`	`10da`	`ffff`	`ffff`	Z, N	1
BYTE-ORIENTED SKIP INSTRUCTIONS
CPFSEQ	f, a	Compare f with WREG, skip if =	1 – 4	`0110`	`001a`	`ffff`	`ffff`	None	1, 2
CPFSGT	f, a	Compare f with WREG, skip if >	1 – 4	`0110`	`010a`	`ffff`	`ffff`	None	1, 2
CPFSLT	f, a	Compare f with WREG, skip if <	1 – 4	`0110`	`000a`	`ffff`	`ffff`	None	1, 2
DECFSZ	f, d, a	Decrement f, Skip if 0	1 – 4	`0010`	`11da`	`ffff`	`ffff`	None	1, 2
DCFSNZ	f, d, a	Decrement f, Skip if Not 0	1 – 4	`0100`	`11da`	`ffff`	`ffff`	None	1, 2
INCFSZ	f, d, a	Increment f, Skip if 0	1 – 4	`0011`	`11da`	`ffff`	`ffff`	None	1, 2
INFSNZ	f, d, a	Increment f, Skip if Not 0	1 – 4	`0100`	`10da`	`ffff`	`ffff`	None	1, 2
TSTFSZ	f, a	Test f, skip if 0	1 – 4	`0110`	`011a`	`ffff`	`ffff`	None	1, 2
BIT-ORIENTED FILE REGISTER INSTRUCTIONS
BCF	f, b, a	Bit Clear f	1	`1001`	`bbba`	`ffff`	`ffff`	None	1
BSF	f, b, a	Bit Set f	1	`1000`	`bbba`	`ffff`	`ffff`	None	1
BTG	f, b, a	Bit Toggle f	1	`0111`	`bbba`	`ffff`	`ffff`	None	1
BIT-ORIENTED SKIP INSTRUCTIONS
BTFSC	f, b, a	Bit Test f, Skip if Clear	1 – 4	`1011`	`bbba`	`ffff`	`ffff`	None	1, 2
BTFSS	f, b, a	Bit Test f, Skip if Set	1 – 4	`1010`	`bbba`	`ffff`	`ffff`	None	1, 2
CONTROL INSTRUCTIONS
BC	n	Branch if Carry	1 – 2	`1110`	`0010`	`nnnn`	`nnnn`	None	2
BN	n	Branch if Negative	1 – 2	`1110`	`0110`	`nnnn`	`nnnn`	None	2
BNC	n	Branch if Not Carry	1 – 2	`1110`	`0011`	`nnnn`	`nnnn`	None	2
BNN	n	Branch if Not Negative	1 – 2	`1110`	`0111`	`nnnn`	`nnnn`	None	2
BNOV	n	Branch if Not Overflow	1 – 2	`1110`	`0101`	`nnnn`	`nnnn`	None	2
BNZ	n	Branch if Not Zero	1 – 2	`1110`	`0001`	`nnnn`	`nnnn`	None	2
BOV	n	Branch if Overflow	1 – 2	`1110`	`0100`	`nnnn`	`nnnn`	None	2
BRA	n	Branch Unconditionally	2	`1101`	`0nnn`	`nnnn`	`nnnn`	None	2
BZ	n	Branch if Zero	1 – 2	`1110`	`0000`	`nnnn`	`nnnn`	None	2
CALL	k, s	Call subroutine	2	`1110`	`110s`	`kkkk`	`kkkk`	None	2, 3
CALL	k, s	Call subroutine	2	`1111`	`kkkk`	`kkkk`	`kkkk`	None	2, 3
CALLW	—	Call subroutine using WREG	2	`0000`	`0000`	`0001`	`0100`	None	2
GOTO	k	Go to address	2	`1110`	`1111`	`kkkk`	`kkkk`	None	3
GOTO	k	Go to address	2	`1111`	`kkkk`	`kkkk`	`kkkk`	None	3
RCALL	n	Relative Call	2	`1101`	`1nnn`	`nnnn`	`nnnn`	None	2
RETFIE	s	Return from interrupt enable	2	`0000`	`0000`	`0001`	`000s`	INTCONx STAT bits	2
RETLW	k	Return with literal in WREG	2	`0000`	`1100`	`kkkk`	`kkkk`	None	2
RETURN	s	Return from Subroutine	2	`0000`	`0000`	`0001`	`001s`	None	2
INHERENT INSTRUCTIONS
CLRWDT	—	Clear Watchdog Timer	1	`0000`	`0000`	`0000`	`0100`	TO, PD
DAW	—	Decimal Adjust WREG	1	`0000`	`0000`	`0000`	`0111`	C
NOP	—	No Operation	1	`0000`	`0000`	`0000`	`0000`	None
NOP	—	No Operation	1	`1111`	`xxxx`	`xxxx`	`xxxx`	None	3
POP	—	Pop top of return stack (TOS)	1	`0000`	`0000`	`0000`	`0110`	None
PUSH	—	Push top of return stack (TOS)	1	`0000`	`0000`	`0000`	`0101`	None
RESET	—	Software device Reset	1	`0000`	`0000`	`1111`	`1111`	All
SLEEP	—	Go into Standby mode	1	`0000`	`0000`	`0000`	`0011`	TO, PD
LITERAL INSTRUCTIONS
ADDFSR	f_n, k	Add FSR (f_n) with literal (k)	1	`1110`	`1000`	`f_nf_nkk`	`kkkk`	None
ADDLW	k	Add literal and WREG	1	`0000`	`1111`	`kkkk`	`kkkk`	C, DC, Z, OV, N
ANDLW	k	AND literal with WREG	1	`0000`	`1011`	`kkkk`	`kkkk`	Z, N
IORLW	k	Inclusive OR literal with WREG	1	`0000`	`1001`	`kkkk`	`kkkk`	Z, N
LFSR	f_n, k	Load FSR(f_n) with a 14-bit literal (k)	2	`1110`	`1110`	`00f_nf_n`	`kkkk`	None	3
LFSR	f_n, k	Load FSR(f_n) with a 14-bit literal (k)	2	`1111`	`00kk`	`kkkk`	`kkkk`	None	3
MOVLB	k	Move literal to BSR<5:0>	1	`0000`	`0001`	`00kk`	`kkkk`	None
MOVLW	k	Move literal to WREG	1	`0000`	`1110`	`kkkk`	`kkkk`	None
MULLW	k	Multiply literal with WREG	1	`0000`	`1101`	`kkkk`	`kkkk`	None
RETLW	k	Return with literal in WREG	2	`0000`	`1100`	`kkkk`	`kkkk`	None
SUBFSR	f_n, k	Subtract literal (k) from FSR (f_n)	1	`1110`	`1001`	`f_nf_nkk`	`kkkk`	None
SUBLW	k	Subtract WREG from literal	1	`0000`	`1000`	`kkkk`	`kkkk`	C, DC, Z, OV, N
XORLW	k	Exclusive OR literal with WREG	1	`0000`	`1010`	`kkkk`	`kkkk`	Z, N
DATA MEMORY – PROGRAM MEMORY INSTRUCTIONS
TBLRD*	—	Table Read	2	`0000`	`0000`	`0000`	`1000`	None
TBLRD*+	—	Table Read with post-increment	2	`0000`	`0000`	`0000`	`1001`	None
TBLRD*-	—	Table Read with post-decrement	2	`0000`	`0000`	`0000`	`1010`	None
TBLRD+*	—	Table Read with pre-increment	2	`0000`	`0000`	`0000`	`1011`	None
TBLWT*	—	Table Write	2	`0000`	`0000`	`0000`	`1100`	None
TBLWT*+	—	Table Write with post-increment	2	`0000`	`0000`	`0000`	`1101`	None
TBLWT*-	—	Table Write with post-decrement	2	`0000`	`0000`	`0000`	`1110`	None
TBLWT+*	—	Table Write with pre-increment	2	`0000`	`0000`	`0000`	`1111`	None
Note: When a PORT register is modified as a function of itself (e.g., `MOVF PORTB, 1, 0`), the value used will be that value present on the pins themselves. For example, if the data latch is ‘`1`’ for a pin configured as input and is driven low by an external device, the data will be written back with a ‘`0`’. If Program Counter (PC) is modified or a conditional test is true, the instruction requires two cycles. The second cycle is executed as a `NOP`. Some instructions are multi-word instructions. The extra words of these instructions will be executed as a `NOP` unless the first word of the instruction retrieves the information embedded in these 16 bits. This ensures that all program memory locations have a valid instruction. f_s and f_d do not cover the full memory range. 2 MSbs of bank selection are forced to `0b00` to limit the range of these instructions to the lower 4k addressing space.