Array putting garbage in register

Locash · 02 March 2018, 00:02

Good evening all,

Sorry this is probably really simple but its been bugging me all day. I'm trying to populate an array with some colour values then point A2 at them. I'm not getting any compiler (AsmTwo) errors but looking at the value of A2 it just shows the value CCC.

e.g.

lea colour,a2

colour: dc.w $100,$200,$300,$400,$500 etc

Any thoughts or pointers? har har

Galahad/FLT · 02 March 2018, 00:08

Whats the entirety of your list of colours? Is one of them $ccc?

Locash · 02 March 2018, 00:09

Its just a straight run of $100,$200,$300,$400,$500,$600,$700,$800,$900,$a00,$b00,$c00,$d00,$e00,$f00 to get a red fade. I have attached the whole code, following Protons guide but im trying to wander a bit.

Galahad/FLT · 02 March 2018, 00:41

That code you just listed works fine, show me the code that doesn't.

StingRay · 02 March 2018, 00:46

I can't see that you access any values in your color table at all. Hint: what would a move.w (a2)+,d0 do?

Locash · 02 March 2018, 00:50

Sorry both i'm a bit shamefaced here, I just did a moveq #11,d2 and I see the correct value. It appears I'm not understanding how the output of AsmTwo displays data it seems. What was confusing me was when i exited the programe, AsmTwo was displaying CCC for the value of A2, I was expecting it to show $100 as the value for A2 as i had not advanced it. (sorry if im getting the terminology wrong)

Stingray, I think it moves the contents of A2 to D0 then increments A2 by two?

Sorry another edit. Ok i get it now, CCC is the memory address that A2 is pointing to, not the first value of the array like I expected. If i look in the debugger I see all the values I stored starting at CCC through to CDB!. Assume this is because its an address register and not a data register..

Locash · 04 March 2018, 12:05

Morning all, sorry another question.

In the attached code in the copper block, where i set the line to white with dc.w $180,$fff. If i change it to a move.w #$fff,$dff180 the rest of the copper executes successfully (top and bottom colour change borders are there but the white line isn't drawn. The HRM says copper accepts moves, waits and skips so i'm unsure why the line is not there. Any thoughts as to why the move isn't working? Thanks

phx · 04 March 2018, 12:52

???
The copper does not understand 68000 code.

When the HRM says it understands Move instructions, then it is refering to the Copper Move instruction, which is an even register in the first word and the value in the second word.

Locash · 04 March 2018, 13:03

Ahh ok, I understand now. Thanks PHX, I think i need to play some more with the basics first

02 March 2018, 00:50	#6
Locash Registered User Join Date: Oct 2003 Location: Sunny Wales Posts: 100	Sorry both i'm a bit shamefaced here, I just did a moveq #11,d2 and I see the correct value. It appears I'm not understanding how the output of AsmTwo displays data it seems. What was confusing me was when i exited the programe, AsmTwo was displaying CCC for the value of A2, I was expecting it to show $100 as the value for A2 as i had not advanced it. (sorry if im getting the terminology wrong) Stingray, I think it moves the contents of A2 to D0 then increments A2 by two? Sorry another edit. Ok i get it now, CCC is the memory address that A2 is pointing to, not the first value of the array like I expected. If i look in the debugger I see all the values I stored starting at CCC through to CDB!. Assume this is because its an address register and not a data register.. Last edited by Locash; 02 March 2018 at 01:26.

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02 March 2018, 00:02	#1
Locash Registered User Join Date: Oct 2003 Location: Sunny Wales Posts: 100	Array putting garbage in register Good evening all, Sorry this is probably really simple but its been bugging me all day. I'm trying to populate an array with some colour values then point A2 at them. I'm not getting any compiler (AsmTwo) errors but looking at the value of A2 it just shows the value CCC. e.g. lea colour,a2 colour: dc.w $100,$200,$300,$400,$500 etc Any thoughts or pointers? har har

02 March 2018, 00:08	#2
Galahad/FLT Going nowhere Join Date: Oct 2001 Location: United Kingdom Age: 50 Posts: 8,986	Whats the entirety of your list of colours? Is one of them $ccc?

02 March 2018, 00:41	#4
Galahad/FLT Going nowhere Join Date: Oct 2001 Location: United Kingdom Age: 50 Posts: 8,986	That code you just listed works fine, show me the code that doesn't.

02 March 2018, 00:46	#5
StingRay move.l #$c0ff33,throat Join Date: Dec 2005 Location: Berlin/Joymoney Posts: 6,863	I can't see that you access any values in your color table at all. Hint: what would a move.w (a2)+,d0 do?

04 March 2018, 12:05	#7
Locash Registered User Join Date: Oct 2003 Location: Sunny Wales Posts: 100	Morning all, sorry another question. In the attached code in the copper block, where i set the line to white with dc.w $180,$fff. If i change it to a move.w #$fff,$dff180 the rest of the copper executes successfully (top and bottom colour change borders are there but the white line isn't drawn. The HRM says copper accepts moves, waits and skips so i'm unsure why the line is not there. Any thoughts as to why the move isn't working? Thanks

04 March 2018, 12:52	#8
phx Natteravn Join Date: Nov 2009 Location: Herford / Germany Posts: 2,496	??? The copper does not understand 68000 code. When the HRM says it understands Move instructions, then it is refering to the Copper Move instruction, which is an even register in the first word and the value in the second word.

04 March 2018, 13:03	#9
Locash Registered User Join Date: Oct 2003 Location: Sunny Wales Posts: 100	Ahh ok, I understand now. Thanks PHX, I think i need to play some more with the basics first

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