How to force the carry flag to 1 ?

Bean

Okay, we've been before, but I cannot find the thread.

I need 1 instruction that will set the carry flag without have any specific value in any variable.

In my notes I have:

· rol $,#0 WC,NR·· 'set c flag (because b31=1)

But that doesn't seem right because bit 31 is NOT a 1 for the rol instruction.

The only instruction I see that might work is:

·CMPSUB $,$ WC, NR

It seem kind of strange to set the carry flag if the values are =·doesn't it ??? This isn't a typo·in the manual is it ?

Bean

·

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Phil Pilgrim (PhiPi)

Bean said...
It seem kind of strange to set the carry flag if the values are = doesn't it ??? This isn't a typo in the manual is it ?

That's what I thought, too, when I first saw it; but it's no typo. It was designed that way to facilitate division.

-Phil

Ale

I thought the mov method was the better one...

mov 0, $ wc, nr

it writes the C with the value at bit 31, set for the mov instruction...

quoting the manual (v1.1) for cmpsub "If the WC effect is specified, the C flag is set (1) if a subtraction is possible (Value1 is equal to or greater than Value2).".

Edit: Phil is right.

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Phil Pilgrim (PhiPi)

BTW, here's the thread you might have been looking for: http://forums.parallax.com/showthread.php?p=764220.

-Phil

Bean

Thanks guys.
Yeah, I prefer the MOV instruction too. It's just a simpler instruction.

I wish Parallax would put a set of prefered instructions in the manual for setting/clearing the carry and zero flag.
P.S. Yes Phil, that is the thread I was looking for.

Bean

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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Use BASIC on the Propeller with the speed of assembly language.
PropBASIC thread http://forums.parallax.com/showthread.php?p=867134

March 2010 Nuts and Volts article·http://www.parallax.com/Portals/0/Downloads/docs/cols/nv/prop/col/nvp5.pdf
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There are two rules in life:
· 1) Never divulge all information
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If you choose not to decide, you still have made a choice. [noparse][[/noparse]RUSH - Freewill]

Post Edited (Bean) : 5/19/2010 2:48:03 PM GMT

Ale

I wanted to suggest that thread too. Phil made a great contribution... is the thread in the wiki already ?

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Visit some of my articles at Propeller Wiki:
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pPropellerSim - A propeller simulator for ASM development sourceforge.net/projects/ppropellersim

Phil Pilgrim (PhiPi)

Once we get macros and #INCLUDE files, we can define our own setc, clrz, etc. instructions in a separate file and be done with it, without having to look them up every time.

-Phil

Cluso99

How true Phil. I thought OBC was going to add it to the cookbook?

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