P12C508 datasheet(42/84 Pages) MICROCHIP

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PIC12C5XX

DS40139A-page 42

Advanced Information

COMF

Complement f

Syntax:

[

label ] COMF

f,d

Operands:

≤ f ≤ 31

∈ [0,1]

Operation:

(f)

→ (dest)

Status Affected:

Encoding:

0010

01df

ffff

Description:

The contents of register 'f' are comple-

mented. If 'd' is 0 the result is stored in

the W register. If 'd' is 1 the result is

stored back in register 'f'.

Words:

Cycles:

Example:

COMF

REG1,0

Before Instruction

REG1

0x13

After Instruction

REG1

0x13

0xEC

DECF

Decrement f

Syntax:

[

label ] DECF f,d

Operands:

≤ f ≤ 31

∈ [0,1]

Operation:

(f) – 1

→ (dest)

Status Affected:

Encoding:

0000

11df

ffff

Description:

Decrement register 'f'. If 'd' is 0 the

result is stored in the W register. If 'd' is

1 the result is stored back in register 'f'.

Words:

Cycles:

Example:

DECF

CNT,

Before Instruction

CNT

0x01

After Instruction

CNT

0x00

DECFSZ

Decrement f, Skip if 0

Syntax:

[

label ] DECFSZ f,d

Operands:

≤ f ≤ 31

∈ [0,1]

Operation:

(f) – 1

→ d; skip if result = 0

Status Affected:

None

Encoding:

0010

11df

ffff

Description:

The contents of register 'f' are decre-

mented. If 'd' is 0 the result is placed in

the W register. If 'd' is 1 the result is

placed back in register 'f'.

If the result is 0, the next instruction,

which is already fetched, is discarded

and an NOP is executed instead mak-

ing it a two cycle instruction.

Words:

Cycles:

1(2)

Example:

HERE

DECFSZ

CNT, 1

GOTO

LOOP

CONTINUE •

•

Before Instruction

address

(HERE)

After Instruction

CNT

CNT - 1;

if CNT

address (CONTINUE);

if CNT

≠

address (HERE+1)

GOTO

Unconditional Branch

Syntax:

[

label ]

GOTO k

Operands:

≤ k ≤ 511

Operation:

→ PC<8:0>;

STATUS<6:5>

→ PC<10:9>

Status Affected:

None

Encoding:

101k

kkkk

Description:

GOTO

is an unconditional branch. The

9-bit immediate value is loaded into PC

bits <8:0>. The upper bits of PC are

loaded from STATUS<6:5>. GOTO is a

two cycle instruction.

Words:

Cycles:

Example:

GOTO THERE

After Instruction

PC =

address

(THERE)

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