How do you set or clear the C or Z flag ?

Bean · 2009-09-05 20:15

I haven't seen anywhere, how do you set or clear the C - Carry and/or the Z - Zero flags ?

Bean.

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Does that byte of memory hold "A", 65, $41 or %01000001 ?
Yes it does...

·

Leon · 2009-09-05 20:49

TEST and TESTN look as though they will do it with appropriate operands.

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

Mike Green · 2009-09-05 21:03

The Carry and Zero flags are available to hold the result for a lot of the instructions. You have to have the instruction bits set that copy these results into the actual flag latches (WC and/or WZ).

Phil Pilgrim (PhiPi) · 2009-09-05 21:07

        [s]mov     any,#1 wc,nr    'Set carry.[/s] [i]See my later post.[/i]
        [s]mov     any,#0 wc,nr    'Clear carry.[/s]
        mov     any,#1 wz,nr    'Clear zero.
        mov     any,#0 wz,nr    'Set zero.

-Phil

Post Edited (Phil Pilgrim (PhiPi)) : 9/5/2009 9:56:42 PM GMT

jazzed · 2009-09-05 21:45

Oooooops ... "mov any,#1 wc,nr" won't set carry. You have to have bit 31 set for mov to set carry. I don't see a one instruction solution ....

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--Steve

Propeller Tools

Post Edited (jazzed) : 9/5/2009 9:52:56 PM GMT

Phil Pilgrim (PhiPi) · 2009-09-05 21:53

Whoa, oops is right! My bad. I was thinking parity.

Okay, try this:

        cmpsub  any,#0 wc,nr    'Set carry.
        cmp       any,#0 wc        'Clear carry.

-Phil

mpark · 2009-09-05 21:56

mov $, $ wc, nr ' sets c

Someone attributed this trick to Phil, but apparently he forgot it.

jazzed · 2009-09-05 21:56

> cmpsub any,#0 wc,nr 'Set carry.

Ok, but what if any contains 0 ?

yes, "mov $, $ wc,nr" sets it.

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--Steve

Propeller Tools

Phil Pilgrim (PhiPi) · 2009-09-05 22:00

jazzed,

That's okay, because 0 => 0. The carry condition is "greater than or equal".

mpark,

Yes, apparently I did. I like cmpsub better, anyway, since it's less obscure. Of course, if we had macros, it wouldn't matter.

-Phil

jazzed · 2009-09-05 22:05

Yup. RTFM [noparse]:)[/noparse]

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--Steve

Propeller Tools

Beau Schwabe · 2009-09-06 00:15

Bean,

There's probably several ways to do this as have already been suggested... here is what I have used...

             Xor       One,     One             nr,wz   'Set_Z
             And       One,     One             nr,wz   'Clr_Z
             Sub       Zero,    One             nr,wc   'Set_C
             Sub       Zero,    Zero            nr,wc   'Clr_C


Zero         long      0
One          long      1

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Post Edited (Beau Schwabe (Parallax)) : 9/6/2009 1:51:52 AM GMT

Cluso99 · 2009-09-06 02:33

There is another thread discussing this without using any longs. Also, I believe the wiki has info as well. OBC's cookbook may have some info as well.

For instance
mov $,#0 wz,nr·· 'set z flag
mov $,#0 wz,nr···'reset z flag
rol·· $,#0 wc,nr·· 'set c flag (because b31=1)
ror· ·$,#0 wc,nr·· 'reset·c flag (because b0=0)
cmp $,$·· wz,wc· 'reset c & set z (because ==)

I posted a whole set a while back - I am looking for it now - should have kept a copy :-(

If you have the c & z flags saved in b31 & b30 respectively

cz_flags long 0-0·· 'b31=c, b30=z, other bits=0

shl· cz_flags,#1·· wc,wz,nr· 'sets/resets both c & z

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade, RetroBlade,·TwinBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: Micros eg Altair, and Terminals eg VT100 (Index) ZiCog (Z80) , MoCog (6809)
· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

Post Edited (Cluso99) : 9/6/2009 3:17:33 AM GMT

Phil Pilgrim (PhiPi) · 2009-09-06 03:15

I finally found the thread I did on this awhile back: http://forums.parallax.com/showthread.php?p=764220. Is it just me, or is search.parallax.com still a little cranky from its recent reindexing?

-Phil

This reminds me of the Perl users' mantra: TMTOWTDI.

Post Edited (Phil Pilgrim (PhiPi)) : 9/6/2009 3:21:47 AM GMT

Cluso99 · 2009-09-06 05:38

I have been having problems too, but likewise don't know if there is a problem. Anyway, here are some more links...
http://forums.parallax.com/forums/default.aspx?f=25&p=6&m=114128
http://forums.parallax.com/forums/attach.aspx?a=17267

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Links to other interesting threads:

· Home of the MultiBladeProps: TriBlade,·RamBlade, RetroBlade,·TwinBlade,·SixBlade, website
· Single Board Computer:·3 Propeller ICs·and a·TriBladeProp board (ZiCog Z80 Emulator)
· Prop Tools under Development or Completed (Index)
· Emulators: Micros eg Altair, and Terminals eg VT100 (Index) ZiCog (Z80) , MoCog (6809)
· Search the Propeller forums·(uses advanced Google search)
My cruising website is: ·www.bluemagic.biz·· MultiBladeProp is: www.bluemagic.biz/cluso.htm

How do you set or clear the C or Z flag ?

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