NEGW

Negate word (Logical 2’s Complement)

NEGW

Syntax

NEGW dst

e.g. NEGW X

Operation

dst <= (dst XOR FFFF) + 1, or 0000 - dst

Description

The destination word is read, then each bit is toggled (inverted), and the

result is incremented before it is written at the destination word. The

destination is an index register.

Instruction overview.

mnem

dst

Affected condition flags

V

I1

H

I0

N

Z

C

NEGW

X

V

-

-

-

N

Z

C

NEGW

Y

V

-

-

-

N

Z

C

V

R15.R14.R13.R12.R11.R10.R9.R8.R7.R6.R5.R4.R3.R2.R1.R0

Set if there is an arithmetic overflow on the 16-bit representation. The V bit

will set when the content of "dst" was $8000 prior to the NEGW operation,

cleared otherwise.

N

R15

Set if bit 7 of the result is set (negative value), cleared otherwise.

Z

R15.R14.R13.R12.R11.R10.R9.R8.R7.R6.R5.R4.R3.R2.R1.R0

Set if the result is zero (0x00), cleared otherwise.

C

R15+R14+R13+R12+R11+R10+R9+R8+R7+R6+R5+R4+R3+R2+R1+R0

Set if a borrow in the implied subtraction from zero, cleared otherwise. The

C bit will be set in all cases except when the contents of "dst" was $0000

prior to the NEGW operation.

Detailed description

dst

Asm

cy

lgth

Op-code(s)

ST7

X

NEGW X

2

1

50

Y

NEGW Y

2

2

90

50

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STM8 instruction set

PM0044

mnem

Affected condition flags

V

I1

H

I0

N

Z

C

NOP

-

-

-

-

-

-

-

Detailed description

Addressing

Asm

cy

lgth

Op-code(s)

ST7

mode

Inherent

NOP

1

1

9D

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Doc ID 13590 Rev 3

OR

Logical OR

OR

Syntax

OR A,src

e.g. OR A,#%00110101

Operation

A <= A OR src

Description

The source byte, is logically ORed with the contents of the accumulator

and the result is stored in the accumulator. The source is a memory or data

byte.

Truth table

OR

0

1

0

0

1

1

1

1

Instruction overview

mnem

dst

src

Affected condition flags

V

I1

H

I0

N

Z

C

OR

A

Mem

-

-

-

-

N

Z

-

N

R7

Set if bit 7 of the result is set (negative value), cleared otherwise.

Z

R7.R6.R5.R4.R3.R2.R1.R0

Set if the result is zero (0x00), cleared otherwise.

Detailed description

dst

src

Asm

cy

lgth

Op-code(s)

ST7

A

#byte

OR A,#$55

1

2

AA

XX

A

shortmem

OR A,$10

1

2

BA

XX

A

longmem

OR A,$1000

1

3

CA

MS

LS

A

(X)

OR A,(X)

1

1

FA

A

(shortoff,X)

OR A,($10,X)

1

2

EA

XX

A

(longoff,X)

OR A,($1000,X)

1

3

DA

MS

LS

A

(Y)

OR A,(Y)

1

2

90

FA

A

(shortoff,Y)

OR A,($10,Y)

1

3

90

EA

XX

A

(longoff,Y)

OR A,($1000,Y)

1

4

90

DA

MS

LS

A

(shortoff,SP)

OR A,($10,SP)

1

2

1A

XX

A

[shortptr.w]

OR A,[$10.w]

4

3

92

CA

XX

A

[longptr.w]

OR A,[$1000.w]

4

4

72

CA

MS

LS

A

([shortptr.w],X)

OR A,([$10.w],X)

4

3

92

DA

XX

A

([longptr.w],X)

OR A,([$1000.w],X)

4

4

72

DA

MS

LS

A

([shortptr.w],Y)

OR A,([$1000],Y)

4

3

91

DA

XX

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STM8 instruction set

PM0044

POP

Pop from stack

POP

Syntax

POP dst

e.g. POP CC

Operation

dst <= (++SP)

Description

Restore from the stack a data byte which will be placed in dst location. The

stack pointer is incremented by one. This instruction is used to restore a

register/memory value.

mnem

dst

Affected condition flags

V

I1

H

I0

N

Z

C

POP

A

-

-

-

-

-

-

-

POP

CC

V

I1

H

I0

N

Z

C

POP

Mem

-

-

-

-

-

-

-

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Doc ID 13590 Rev 3