Microchip Technology MCP1630DM-DDBS1 Data Sheet

©

 2007 Microchip Technology Inc.

DS41211D-page 101

The PIC12F683 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
is presented in Figure 13-1, while the various opcode
fields are summarized in Table 13-1.

Table 13-2 lists the instructions recognized by the
MPASM

TM

 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.

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
operation, while ‘f’ represents the address of the file in
which the bit is located.

For  literal and control operations, ‘k’ represents an
8-bit or 11-bit constant, or literal value.

One instruction cycle consists of four oscillator periods;
for an oscillator frequency of 4 MHz, this gives a
nominal instruction execution time of 1

μ

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

.

All instruction examples use the format ‘

0xhh

’ to

represent a hexadecimal number, where ‘

h

’ signifies a

hexadecimal digit.

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.

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.

f

Register file address (0x00 to 0x7F)

W

Working register (accumulator)

b

Bit address within an 8-bit file register

k

Literal field, constant data or label

x

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.

d

Destination select; d = 

0

: store result in 

W

,

d = 

1

: store result in file register f. 

Default is d = 

1.

PC

Program Counter

TO

Time-out bit

C

Carry bit

DC

Digit carry bit

Z

Zero bit

PD

Power-down bit

13                          8     7    6                              0

d = 

0

 for destination W

OPCODE                 d              f (FILE #)

d = 

1

 for destination f

f = 7-bit file register address

13                         10  9        7   6                       0

OPCODE          b (BIT #)        f (FILE #)

b = 3-bit bit address
f = 7-bit file register address

13                                  8    7                             0

OPCODE                              k (literal)

k = 8-bit immediate value

13                 11    10                                          0

OPCODE                        k (literal)

k = 11-bit immediate value

General

CALL

 and 

GOTO

 instructions only