nesdev.com

I would like to peek into the stack to get a value N bytes from the top of the stack.
But I cannot find an example for this.

Is there some syntax like in NESASM similar to NASM's where you can get a value at an address that is the sum of a register plus a certain value?
Similar to this:

The plain 6502 has no stack-indexed instructions, unfortunately.

You basically have to save or discard the contexts of X, use the TSX instruction, and use instructions that use absolute-indexed addressing like LDA $0100,X

This is one of the many reasons that cc65 uses a separate software stack for function parameters, instead of using the same stack as the one that holds return addresses.

On 6502 (NES), you would indeed use TSX and index into the stack that way. Just watch for wraparound if there aren't already $10 bytes pushed to the stack.

On 65816 (Super NES), the stack behaves more like an ordinary index register in that you can use LDA $10,S, or even LDA ($10,S),Y.

The most common way to read the Nth element from the top of the stack is:

See my 6502 stacks treatise. (Notice it's "stacks," plural, as it includes virtual stacks, and is not limited to just the page-1 hardware stack.) There's all you'd ever want to know about 6502 stacks there, plus more, in 19 chapters plus appendices. Indexing into the page-1 hardware stack is introduced in chapter 5, at http://wilsonminesco.com/stacks/stackaddressing.html .

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http://WilsonMinesCo.com/ lots of 6502 resources