PIC16F818/819
13.0
INSTRUCTION SET SUMMARY
The PIC16 instruction set is highly orthogonal and is
comprised of three basic categories:
•
Byte-oriented
operations
•
Bit-oriented
operations
•
Literal and control
operations
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
are presented in Figure 13-1, while the various opcode
fields are summarized in Table 13-1.
MPASM
TM
assembler. A complete description of each
instruction is also available in the
“PICmicro
®
Mid-Range
MCU Family Reference Manual”
(DS33023).
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.
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.
For
bit-oriented
instructions, ‘b’ represents a bit field
designator, which selects the bit affected by the opera-
tion, while ‘f’ represents the address of the file in which
the bit is located.
For
literal and control
operations, ‘k’ represents an
eight or eleven-bit constant or literal value
One instruction cycle consists of four oscillator periods.
For an oscillator frequency of 4 MHz, this gives a nor-
mal 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.
Note:
To maintain upward compatibility with
future PIC16F818/819 products, do not
use the
OPTION
and
TRIS
instructions.
For example, a “CLRF
PORTB”
instruction will read
PORTB, clear all the data bits, then write the result
back to PORTB. This example would have the
unintended result that the condition that sets the RBIF
flag would be cleared.
TABLE 13-1:
Field
f
W
b
k
x
OPCODE FIELD
DESCRIPTIONS
Description
Register file address (0x00 to 0x7F)
Working register (accumulator)
Bit address within an 8-bit file register
Literal field, constant data or label
Don’t care location (=
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.
Destination select; d =
0:
store result in W,
d =
1:
store result in file register f.
Default is d =
1.
Program Counter
Time-out bit
Power-Down bit
d
PC
TO
PD
FIGURE 13-1:
GENERAL FORMAT FOR
INSTRUCTIONS
0
Byte-oriented file register operations
13
8 7 6
OPCODE
d
f (FILE #)
d =
0
for destination W
d =
1
for destination f
f = 7-bit file register address
Bit-oriented file register operations
13
10 9
7 6
OPCODE
b (BIT #)
f (FILE #)
b = 3-bit bit address
f = 7-bit file register address
Literal and control operations
General
13
OPCODE
k = 8-bit immediate value
CALL
and
GOTO
instructions only
13
11
OPCODE
10
k (literal)
8
7
k (literal)
0
All instruction examples use the format ‘0xhh’ to
represent a hexadecimal number, where ‘h’ signifies a
hexadecimal digit.
0
13.1
READ-MODIFY-WRITE
OPERATIONS
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 instruction or
the destination designator ‘d’. A read operation is
performed on a register even if the instruction writes to
that register.
2004 Microchip Technology Inc.
0
k = 11-bit immediate value
DS39598E-page 103
MICROCHIP [ MICROCHIP TECHNOLOGY ]
