a really newbie question...

[ehguacho]

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?

[BigEd]

Result is stored in the Accumulator. Some assemblers allow 'ASL' as a legal opcode, some 'ASL A'

Cheers
Ed

[ehguacho]

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?

[leeeeee]

The result of an ASL always overwrites the original data.

Lee.

[ehguacho]

leeeeee wrote:

The result of an ASL always overwrites the original data.

Lee.

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

[GARTHWILSON]

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 .

[ehguacho]

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)

[GARTHWILSON]

Yes, and also affects the N, Z, and C flags the same as ASL A.

[ehguacho]

ok thanks!