flags

Unknown

Hi.

Can you tell me what i have to use the A,S,P and O flag for.

Ren

Unknown

: Hi.

: Can you tell me what i have to use the A,S,P and O flag for.

: Ren

AF - Auxiliary Carry Flag, Some math operations?

SF - Sign flag... enables signed mathematic operations,

I think. (Treating highest bit as the sign)

PF - Parity Flag - Not really sure, I believe this is set if a

parity error in RAM checking occurs. This would trigger a NMI.

OF - Overflow flag - Set if a mathematical operation causes an

overflow. This normally also generates an INT 0h.

None of these flags are very commonly used... for most assembly

tasks, you can safely ignore them.

Matthew Gross

Acheron@Hotmail.com




URL:http://acheronx.ml.org/home/

Unknown

As far as uses, go, each of these flags can come in handy.

The auxilliary carry checks the status of the most significant

4 bits in an 8 bit register, which is very usefull in maths

operations involving BCD or binary coded decimal numbers

(obscure I know).

The sign flag is perhaps the most common flag used in this set,

as it is used for any jump if greater/less than or jump if sign

operations. This is an important flag when dealing with signed

numbers and it is updated after any register or memory operation.

I think the parity flag is set to the parity of the last

operation. This could obviously be used for communications

involving parity calculations.

Finally, the overflow flag is another important flag. As

Matthew said, it report if the previos operation caused an

overflow condition, which is very good for monitoring counters

and also checking the validity of mathematical operations. You

should use this flag if you want robust code.



Hope that helps

aXis

: : Hi.

: : Can you tell me what i have to use the A,S,P and O flag for.

: : Ren

: AF - Auxiliary Carry Flag, Some math operations?

: SF - Sign flag... enables signed mathematic operations,

: I think. (Treating highest bit as the sign)

: PF - Parity Flag - Not really sure, I believe this is set if a

: parity error in RAM checking occurs. This would trigger a NMI.

: OF - Overflow flag - Set if a mathematical operation causes an

: overflow. This normally also generates an INT 0h.

: None of these flags are very commonly used... for most assembly

: tasks, you can safely ignore them.

: Matthew Gross

: Acheron@Hotmail.com