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Clarify behavior of pop_stack
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@ -211,18 +211,15 @@ mos6502_push_stack(mos6502 *cpu, vm_8bit addr)
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}
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/*
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* Pop an address from the stack and return that.
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* Increment the stack register and return the value that is pointed at
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* by the new offset. Because the S register is 8-bit, the following
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* (correct) behavior is exhibited: when S overflows beyond 0xFF, it
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* rolls over to 0x00.
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*/
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vm_8bit
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mos6502_pop_stack(mos6502 *cpu)
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{
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// The first thing we want to do here is to decrement S by 2, since
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// the value we want to return is two positions back.
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cpu->S++;
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// We need to use a bitwise-or operation to combine the hi and lo
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// bytes we retrieve from the stack into the actual position we
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// would use for the PC register.
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return mos6502_get(cpu, 0x0100 + cpu->S);
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}
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