PIC16F630/676
For example, a CLRF PORTA instruction will read
PORTA, clear all the data bits, then write the result back
to PORTA. This example would have the unintended
result of clearing the condition that set the RAIF flag.
10.0 INSTRUCTION SET SUMMARY
The PIC16F630/676 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
Field
Description
Each PIC16 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.
f
W
b
k
x
Register file address (0x00 to 0x7F)
Working register (accumulator)
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 Ref-
erence Manual (DS33023).
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.
d
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.
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
FIGURE 10-1:
GENERAL FORMAT FOR
INSTRUCTIONS
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.
Byte-oriented file register operations
13
8
7
6
0
OPCODE
d
f (FILE #)
For literal and control operations, ‘k’ represents an
8-bit or 11-bit constant, or literal value
d = 0 for destination W
d = 1 for destination f
f = 7-bit file register address
One instruction cycle consists of four oscillator periods;
for an oscillator frequency of 4 MHz, this gives a normal
instruction execution time of 1 μs. 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.
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 TRISinstructions.
Literal and control operations
General
13
8
7
0
0
All instruction examples use the format ‘0xhh’ to
represent a hexadecimal number, where ‘h’signifies
a hexadecimal digit.
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)
© 2007 Microchip Technology Inc.
DS40039E-page 71
MICROCHIP [ MICROCHIP ]
