PIC16F631/677/685/687/689/690
TABLE 15-1: OPCODE FIELD
15.0 INSTRUCTION SET SUMMARY
DESCRIPTIONS
The PIC16F690 instruction set is highly orthogonal and
is comprised of three basic categories:
Field
Description
f
W
b
Register file address (0x00 to 0x7F)
Working register (accumulator)
• Byte-oriented operations
• Bit-oriented operations
• Literal and control operations
Bit address within an 8-bit file register
Literal field, constant data or label
k
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 15-1, while the various opcode
fields are summarized in Table 15-1.
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.
d
Destination select; d = 0: store result in W,
d = 1: store result in file register f.
Default is d = 1.
Table 15-2 lists the instructions recognized by the
MPASMTM assembler.
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.
PC
TO
C
Program Counter
Time-out bit
Carry bit
DC
Z
Digit carry bit
Zero 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.
PD
Power-down bit
FIGURE 15-1:
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
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
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
All instruction examples use the format ‘0xhh’ to
represent a hexadecimal number, where ‘h’ signifies a
hexadecimal digit.
Literal and control operations
General
13
8
7
0
0
15.1 Read-Modify-Write Operations
OPCODE
k (literal)
Any instruction that specifies a file register as part of
the instruction performs a Read-Modify-Write (RMW)
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 = 8-bit immediate value
CALLand GOTOinstructions only
13 11 10
OPCODE
k = 11-bit immediate value
k (literal)
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
consequence of clearing the condition that set the RAIF
flag.
© 2007 Microchip Technology Inc.
DS41262D-page 213
MICROCHIP [ MICROCHIP ]
