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jeffythedragonslayer
PostPosted: Wed May 18, 2022 12:37 am 
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I have reserved a 16-bit variable with .res on the zeropage in ca65, but incrementing it sometimes causes damaging side effects to the rest of my program. I suspect that the memory location it is allocated at is serving double duty. Is there an exhaustive list of all 65816 instructions that modify the ZP anywhere?
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IamRob
PostPosted: Wed May 18, 2022 3:17 am 
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Since you are using a 65816 anyways, maybe consider using a direct-page.

But for a quick reference:

zero page unused memory

FREE - $6.9 $17.19 $1E $86.88 $8B $8D.8E $90 $AE $CE.CF $D5 $D7 $D9 $E3 $EB.EF $FA.FE

Monitor calls use (so user should never use this memory) - $20.4F

Applesoft - $0D.14, $10.16, $4E.4F, $67.84, $B1.CD, $D6, $D8.DE, $F1.F8
Integer Basic - $0D, $4A.DF, FE.FF

Text screen - $20.25, $28.29, $32.33, $F1, $F3
Lores graphics - $28.29, $2C, $30
Hires graphics - $1A.1D, $26.27, $E0.EA, $F9

Prodos - $40.4E
Dos 3.3 - $18.19, $26.2F, 33.46


Basically then, you can consider memory free if you are not using that capability. For instance, I use $E0.EF quite a bit if my program uses the text screen and not the graphics screens.
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gfoot
PostPosted: Wed May 18, 2022 7:47 am 
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Presumably you guys are talking about a specific system here, not the 65816 in general? It would be good to be clear about that.
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Dr Jefyll
PostPosted: Wed May 18, 2022 1:32 pm 
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Quote:
an exhaustive list of all 65816 instructions that modify the ZP

You mean something like this? (I've omitted various instructions that push to stack, but these too could potentially modify "zero page" (ie, Direct Page).

STA STY STX
ROL ROR ASL LSR INC DEC
STZ TSB TRB

-- Jeff

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BigDumbDinosaur
PostPosted: Wed May 18, 2022 2:10 pm 
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IamRob wrote:
Since you are using a 65816 anyways, maybe consider using a direct-page.

But for a quick reference:

zero page unused memory

FREE - $6.9 $17.19 $1E $86.88 $8B $8D.8E $90 $AE $CE.CF $D5 $D7 $D9 $E3 $EB.EF $FA.FE

Monitor calls use (so user should never use this memory) - $20.4F

Applesoft - $0D.14, $10.16, $4E.4F, $67.84, $B1.CD, $D6, $D8.DE, $F1.F8
Integer Basic - $0D, $4A.DF, FE.FF

Text screen - $20.25, $28.29, $32.33, $F1, $F3
Lores graphics - $28.29, $2C, $30
Hires graphics - $1A.1D, $26.27, $E0.EA, $F9

Prodos - $40.4E
Dos 3.3 - $18.19, $26.2F, 33.46


Basically then, you can consider memory free if you are not using that capability. For instance, I use $E0.EF quite a bit if my program uses the text screen and not the graphics screens.

I'm not sure I am following the above. The OP didn't mention the system type.

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jeffythedragonslayer
PostPosted: Wed May 18, 2022 6:03 pm 
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gfoot wrote:
Presumably you guys are talking about a specific system here, not the 65816 in general? It would be good to be clear about that.


It's a Super Nintendo. Thank for the replies; together with viewtopic.php?f=2&t=7130 I'm making progress on this bug.
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BigDumbDinosaur
PostPosted: Wed May 18, 2022 8:23 pm 
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jeffythedragonslayer wrote:
gfoot wrote:
Presumably you guys are talking about a specific system here, not the 65816 in general? It would be good to be clear about that.

It's a Super Nintendo. Thank for the replies; together with viewtopic.php?f=2&t=7130 I'm making progress on this bug.

In the future, it would be a good idea to mention the target system in your first post.

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jeffythedragonslayer
PostPosted: Wed May 18, 2022 11:43 pm 
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BigDumbDinosaur wrote:

In the future, it would be a good idea to mention the target system in your first post.


I thought limiting the conversation to only one particular 65816 system would make the thread less useful.
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IamRob
PostPosted: Thu May 19, 2022 4:35 am 
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BigDumbDinosaur wrote:
IamRob wrote:
Basically then, you can consider memory free if you are not using that capability. For instance, I use $E0.EF quite a bit if my program uses the text screen and not the graphics screens.

I'm not sure I am following the above. The OP didn't mention the system type.

My fault. Had the IIGS tab beside this one and had it in my head when talking about the 65816, it was on the IIGS forum.
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BigDumbDinosaur
PostPosted: Thu May 19, 2022 5:54 am 
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jeffythedragonslayer wrote:
I thought limiting the conversation to only one particular 65816 system would make the thread less useful.

You’re right, it would be limiting. However, when I saw the ][GS stuff I thought that was what you are working with.

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