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Clearer documentation on push_stack
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@ -192,21 +192,15 @@ mos6502_free(mos6502 *cpu)
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}
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/*
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* Push a _16-bit_ number to the stack. Generally speaking, only
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* addresses are pushed to the stack, such that would be contained in
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* the PC register (which is 16-bit).
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*
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* The stack is contained within a single page of memory, so you would
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* be right in observing that the stack can contain at most 128, not
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* 256, addresses.
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* Push an 8-bit value to the stack, and then decrement the S register
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* so that it points at the place where a new value would be deposited
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* by a subsequent push. If S is decremented below 0, it rolls around to
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* FF.
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*/
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void
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mos6502_push_stack(mos6502 *cpu, vm_8bit addr)
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{
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mos6502_set(cpu, 0x100 + cpu->S, addr);
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// And finally we need to increment S by 2 (since we've used two
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// bytes in the stack).
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cpu->S--;
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}
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