PIC18F258-ESLASHLSQTP datasheet(303/402 Pages) MICROCHIP

303 / 402 page

DS41159E-page 301

PIC18FXX8

DECFSZ

Decrement f, Skip if 0

Syntax:

[

label ] DECFSZ f [,d [,a]]

Operands:

≤ f ≤ 255

∈ [0,1]

Operation:

(f) – 1

→ dest,

skip if result = 0

Status Affected:

None

Encoding:

0010

11da

ffff

Description:

The contents of register ‘f’ are

decremented. If ‘d’ is ‘0’, the result is

placed in W. If ‘d’ is ‘1’, the result is

placed back in register ‘f’ (default).

If the result is ‘0’, the next instruction

which is already fetched is discarded

and a NOP is executed instead, making

it a two-cycle instruction. If ‘a’ is ‘0’, the

Access Bank will be selected,

overriding the BSR value. If ‘a’ = 1,

then the bank will be selected as per

the BSR value (default).

Words:

Cycles:

1(2)

Note:

3 cycles if skip and followed

by a 2-word instruction.

Q Cycle Activity:

Decode

Read

Process

Data

Write to

destination

If skip:

operation

If skip and followed by 2-word instruction:

operation

Example:

HERE

DECFSZ

CNT

GOTO

LOOP

CONTINUE

Before Instruction

Address (HERE)

After Instruction

CNT

CNT – 1

If CNT

PC =

Address (CONTINUE)

If CNT

≠

PC =

Address (HERE + 2)

DCFSNZ

Decrement f, Skip if not 0

Syntax:

[

label ] DCFSNZ

f [,d [,a]]

Operands:

≤ f ≤ 255

∈ [0,1]

Operation:

(f) – 1

→ dest,

skip if result

≠ 0

Status Affected:

None

Encoding:

0100

11da

ffff

Description:

The contents of register ‘f’ are

decremented. If ‘d’ is ‘0’, the result is

placed in W. If ‘d’ is ‘1’, the result is

placed back in register ‘f’ (default).

If the result is not ‘0’, the next

instruction which is already fetched is

discarded and a NOP is executed

instead, making it a two-cycle

instruction. If ‘a’ is ‘0’, the Access Bank

will be selected, overriding the BSR

value. If ‘a’ = 1, then the bank will be

selected as per the BSR value

(default).

Words:

Cycles:

1(2)

Note:

3 cycles if skip and followed

by a 2-word instruction.

Q Cycle Activity:

Decode

Read

Process

Data

Write to

destination

If skip:

operation

If skip and followed by 2-word instruction:

operation

Example:

HERE

DCFSNZ TEMP

ZERO

NZERO

Before Instruction

TEMP

After Instruction

TEMP

TEMP – 1,

If TEMP

Address (ZERO)

If TEMP

≠

Address (NZERO)

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