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ehguacho
PostPosted: Tue Mar 16, 2010 5:19 pm 
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just to be sure: in the instruction ASL A (ASL accumulator) the operation is:

1) A = ASL accumulator

...or just

2) ASL accumulator

...???

the result of the ASL operation is stored into the accumulator? or the ASL instruction is just used to set/reset flags?

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BigEd
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PostPosted: Tue Mar 16, 2010 5:26 pm 
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Result is stored in the Accumulator. Some assemblers allow 'ASL' as a legal opcode, some 'ASL A'

Cheers
Ed
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ehguacho
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PostPosted: Tue Mar 16, 2010 5:40 pm 
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BigEd wrote:
Result is stored in the Accumulator. Some assemblers allow 'ASL' as a legal opcode, some 'ASL A'

Cheers
Ed

thanks Ed! i suppose it is also valid for "ASL Zero Page" and all the others ASL's... i mean that the result of any kind of ASL is always stored into the accumulator. is that right?

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leeeeee
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PostPosted: Tue Mar 16, 2010 5:54 pm 
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The result of an ASL always overwrites the original data.

Lee.
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ehguacho
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PostPosted: Tue Mar 16, 2010 6:19 pm 
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leeeeee wrote:
The result of an ASL always overwrites the original data.

Lee.

that means that it may ovewrite memory address... thanks Lee!

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GARTHWILSON
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PostPosted: Tue Mar 16, 2010 6:41 pm 
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Only ASL A leaves the result in the accumulator. ASL done to a memory address does not affect the accumulator. If you don't want it to affect the memory address, then first do LDA then ASL A.

There's a ton of great information in the WDC programming manual downloadable at their website at http://www.westerndesigncenter.com/wdc/ ... manual.pdf .
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ehguacho
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PostPosted: Tue Mar 16, 2010 7:40 pm 
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GARTHWILSON wrote:
Only ASL A leaves the result in the accumulator. ASL done to a memory address does not affect the accumulator.

but it affects the value in the memory address. isn't it? i.e.:

assume $FE is #AA (170 in decimal)

ASL $FE

...after that $FE is #54 (84 in decimal)

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GARTHWILSON
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PostPosted: Tue Mar 16, 2010 7:45 pm 
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Yes, and also affects the N, Z, and C flags the same as ASL A.
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ehguacho
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PostPosted: Tue Mar 16, 2010 9:44 pm 
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ok thanks! :D

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