PIC12F629/675
For example, a CLRF GPIOinstruction will read GPIO,
clear all the data bits, then write the result back to
GPIO. This example would have the unintended result
that the condition that sets the GPIF flag would be
cleared.
10.0 INSTRUCTION SET SUMMARY
The PIC12F629/675 instruction set is highly orthogonal
and is comprised of three basic categories:
• Byte-oriented operations
• Bit-oriented operations
TABLE 10-1: OPCODE FIELD
DESCRIPTIONS
• Literal and control operations
Each PIC12F629/675 instruction is a 14-bit word
divided into an opcode, which specifies the instruction
type, and one or more operands, which further specify
the operation of the instruction. The formats for each of
the categories is presented in Figure 10-1, while the
various opcode fields are summarized in Table 10-1.
Field
Description
f
Register file address (0x00 to 0x7F)
Working register (accumulator)
W
b
k
Bit address within an 8-bit file register
Literal field, constant data or label
Table 10-2 lists the instructions recognized by the
MPASMTM assembler. A complete description of
each instruction is also available in the PIC® Mid-
Range Reference Manual (DS33023).
x
Don’t care location (= 0or 1).
The assembler will generate code with x = 0.
It is the recommended form of use for
compatibility with all Microchip software tools.
For byte-oriented instructions, ‘f’ represents a file
register designator and ‘d’ represents a destination
designator. The file register designator specifies which
file register is to be used by the instruction.
d
Destination select; d = 0: store result in W,
d = 1: store result in file register f.
Default is d = 1.
PC
TO
PD
Program Counter
Time-out bit
The destination designator specifies where the result of
the operation is to be placed. If ‘d’ is zero, the result is
placed in the W register. If ‘d’ is one, the result is placed
in the file register specified in the instruction.
Power-down bit
For bit-oriented instructions, ‘b’ represents a bit field
designator, which selects the bit affected by the
operation, while ‘f’ represents the address of the file in
which the bit is located.
FIGURE 10-1:
GENERAL FORMAT FOR
INSTRUCTIONS
Byte-oriented file register operations
13
8
7
6
0
For literal and control operations, ‘k’ represents an 8-
bit or 11-bit constant, or literal value.
OPCODE
d
f (FILE #)
d = 0for destination W
d = 1for destination f
One instruction cycle consists of four oscillator periods;
for an oscillator frequency of 4 MHz, this gives a normal
instruction execution time of 1 s. All instructions are
executed within a single instruction cycle, unless a
conditional test is true, or the program counter is
changed as a result of an instruction. When this occurs,
the execution takes two instruction cycles, with the
second cycle executed as a NOP.
f = 7-bit file register address
Bit-oriented file register operations
13 10 9
b (BIT #)
7
6
0
OPCODE
f (FILE #)
b = 3-bit bit address
f = 7-bit file register address
Note: To maintain upward compatibility with
future products, do not use the OPTION
and TRISIOinstructions.
Literal and control operations
General
All instruction examples use the format ‘0xhh’ to
represent a hexadecimal number, where ‘h’ signifies a
hexadecimal digit.
13
8
7
0
0
OPCODE
k (literal)
k = 8-bit immediate value
10.1 Read-Modify-Write Operations
CALLand GOTOinstructions only
13 11 10
OPCODE
k = 11-bit immediate value
Any instruction that specifies a file register as part of
the instruction performs a Read-Modify-Write (R-M-W)
operation. The register is read, the data is modified,
and the result is stored according to either the instruc-
tion, or the destination designator ‘d’. A read operation
is performed on a register even if the instruction writes
to that register.
k (literal)
2010 Microchip Technology Inc.
DS41190G-page 71
MICROCHIP [ MICROCHIP ]
