Devpac CWAIT macro

jman · 06 March 2011, 19:35

Hello,

I just noticed a weird behaviour of the CWAIT macro provided from Devpac to handle copper WAITs (along with CMOVE,CSKIP,...).

Example:

Code:

main:
    dc.w    $9031,$fffe
    CWAIT    $31,$90

the CWAIT macro is actually this instruction:

Code:

DC.W ((\2)&$FF)<<8|((\1)&$7F)<<1|1,$FFFE

If I have a look in memory I see:

Code:

9031 FFFE
9063 FFFE <- ?

Why the X value for the copper is reworked as such? I cannot fully grasp what it is done with my "(\1)" param, but I see there's a $7f involved (first usable line of the screen). Can you help me dismember what it is done and why?

Thanks!

Lonewolf10 · 06 March 2011, 23:59

I personally don't use Macro's in my code - just subroutines

I was unaware of that Macro and prefer to write out the copperlist in the normal way (e.g. the first line in your example).

Regards,
Lonewolf10

hitchhikr · 07 March 2011, 01:21

Input value range is [0..127] (&$7f) and it must be word aligned [0..254] so it's multiplied by 2 (<<1) and it's converted to an odd number ([1..255]) by |1.

Check RKM for infos about Copper inner working.

Lonewolf10 · 07 March 2011, 18:36

Quote:

Originally Posted by hitchhikr

Input value range is [0..127] (&$7f) and it must be word aligned [0..254] so it's multiplied by 2 (<<1) and it's converted to an odd number ([1..255]) by |1.

Thanks for the info. I always wondered what <<1 and |1 meant.

Regards,
Lonewolf10

jman · 07 March 2011, 21:16

Quote:

Originally Posted by hitchhikr

Input value range is [0..127] (&$7f) and it must be word aligned [0..254] so it's multiplied by 2 (<<1) and it's converted to an odd number ([1..255]) by |1.
Check RKM for infos about Copper inner working.

ok, thanks for the explaination. I'll load the reference in my laptop and have a sweet bednight reading. If I won't understand, I'll be back here (you won't get rid of me with a simple rtfm :-) )!

06 March 2011, 19:35	#1
jman Registered User Join Date: Nov 2010 Location: . Posts: 382	Devpac CWAIT macro Hello, I just noticed a weird behaviour of the CWAIT macro provided from Devpac to handle copper WAITs (along with CMOVE,CSKIP,...). Example: Code: main: dc.w $9031,$fffe CWAIT $31,$90 the CWAIT macro is actually this instruction: Code: DC.W ((\2)&$FF)<<8\|((\1)&$7F)<<1\|1,$FFFE If I have a look in memory I see: Code: 9031 FFFE 9063 FFFE <- ? Why the X value for the copper is reworked as such? I cannot fully grasp what it is done with my "(\1)" param, but I see there's a $7f involved (first usable line of the screen). Can you help me dismember what it is done and why? Thanks!

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06 March 2011, 23:59	#2
Lonewolf10 AMOS Extensions Developer Join Date: Jun 2007 Location: near Cambridge, UK Age: 44 Posts: 1,924	I personally don't use Macro's in my code - just subroutines I was unaware of that Macro and prefer to write out the copperlist in the normal way (e.g. the first line in your example). Regards, Lonewolf10

07 March 2011, 01:21	#3
hitchhikr Registered User Join Date: Jun 2008 Location: somewhere else Posts: 527	Input value range is [0..127] (&$7f) and it must be word aligned [0..254] so it's multiplied by 2 (<<1) and it's converted to an odd number ([1..255]) by \|1. Check RKM for infos about Copper inner working.

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