PIC12F508_09 datasheet(57/110 Pages) MICROCHIP

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DS41236E-page 57

PIC12F508/509/16F505

8.0

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 12-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 catego-

ries is presented in Figure 8-1, while the various

opcode fields are summarized in Table 8-1.

For byte-oriented instructions, ‘f’ represents a file

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 ‘0’, the result is

placed in the W register. If ‘d’ is ‘1’, 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 number of the bit affected

by the operation, while ‘f’ represents the number of the

file in which the bit is located.

For literal and control operations, ‘k’ represents an

8 or 9-bit constant or literal value.

TABLE 8-1:

OPCODE FIELD

DESCRIPTIONS

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. In this

case, the execution takes two instruction cycles. One

instruction cycle consists of four oscillator periods.

Thus, for an oscillator frequency of 4 MHz, the normal

instruction execution time is 1

μs. If a conditional test is

true or the program counter is changed as a result of an

instruction, the instruction execution time is 2

μs.

Figure 8-1 shows the three general formats that the

instructions can have. All examples in the figure use

the following format to represent a hexadecimal

number:

0xhhh

where ‘h’ signifies a hexadecimal digit.

FIGURE 8-1:

GENERAL FORMAT FOR

INSTRUCTIONS

Field

Description

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

label

Label name

TOS

Top-of-Stack

Program Counter

WDT

Watchdog Timer counter

Time-out bit

Power-down bit

dest

Destination, either the W register or the specified

[ ]

Options

( )

Contents

→

Assigned to

< >

∈

In the set of

italics

User defined term (font is courier)

Byte-oriented file register operations

d = 0 for destination W

OPCODE

f (FILE #)

d = 1 for destination f

f = 5-bit file register address

Bit-oriented file register operations

8 7

5 4

OPCODE

b (BIT #)

f (FILE #)

b = 3-bit bit address

f = 5-bit file register address

Literal and control operations (except GOTO)

OPCODE

k (literal)

k = 8-bit immediate value

Literal and control operations – GOTO instruction

OPCODE

k (literal)

k = 9-bit immediate value

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