DM163006 datasheet(235/320 Pages) MICROCHIP

235 / 320 page

 2001 Microchip Technology Inc.

Advance Information

DS39541A-page 235

PIC18C601/801

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 decre-

mented. If 'd' is 0, the result is

placed in WREG. 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 dis-

carded, 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’ is 1, the Bank will

be selected as per the BSR value.

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 decre-

mented. If 'd' is 0, the result is

placed in WREG. If 'd' is 1, the result

is placed back in register 'f' (default).

If the result is not 0, the next instruc-

tion, 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’ is 1, the Bank will

be selected as per the BSR value.

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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