18F452 datasheet(250/332 Pages) MICROCHIP

250 / 332 page

PIC18FXX2

DS39564B-page 248

 2002 Microchip Technology Inc.

SUBWFB

Subtract W from f with Borrow

Syntax:

[ label ] SUBWFB

f [,d [,a]

Operands:

≤ f ≤ 255

∈ [0,1]

Operation:

(f) – (W) – (C)

→ dest

Status Affected:

N, OV, C, DC, Z

Encoding:

0101

10da

ffff

Description:

Subtract W and the carry flag (bor-

row) from register 'f' (2’s complement

method). If 'd' is 0, the result is stored

in W. If 'd' is 1, the result is stored

back in register 'f' (default). If ’a’ is 0,

the Access Bank will be selected,

overriding the BSR value. If ’a’ is 1,

then the bank will be selected as per

the BSR value (default).

Words:

Cycles:

Q Cycle Activity:

Decode

Read

Process

Data

Write to

destination

Example 1:

SUBWFB

REG, 1, 0

Before Instruction

REG

0x19

(0001 1001)

0x0D

(0000 1101)

After Instruction

REG

0x0C

(0000 1011)

0x0D

(0000 1101)

; result is positive

Example 2:

SUBWFB

REG, 0, 0

Before Instruction

REG

0x1B

(0001 1011)

0x1A

(0001 1010)

After Instruction

REG

0x1B

(0001 1011)

0x00

; result is zero

Example 3:

SUBWFB

REG, 1, 0

Before Instruction

REG

0x03

(0000 0011)

0x0E

(0000 1101)

After Instruction

REG

0xF5

(1111 0100)

; [2’s comp]

0x0E

(0000 1101)

; result is negative

SWAPF

Swap f

Syntax:

[ label ] SWAPF f [,d [,a]

Operands:

≤ f ≤ 255

∈ [0,1]

Operation:

(f<3:0>)

→ dest<7:4>,

(f<7:4>)

→ dest<3:0>

Status Affected:

None

Encoding:

0011

10da

ffff

Description:

The upper and lower nibbles of reg-

ister ’f’ are exchanged. If ’d’ is 0, the

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

result is placed in register ’f’

(default). If ’a’ is 0, the Access

Bank will be selected, overriding

the BSR value. If ’a’ is 1, then the

bank will be selected as per the

BSR value (default).

Words:

Cycles:

Q Cycle Activity:

Decode

Read

Process

Data

Write to

destination

Example:

SWAPF

REG, 1, 0

Before Instruction

REG

0x53

After Instruction

REG

0x35

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