Description:

Pop the top byte off the stack as a relative (from the top) 1-based stack index.  Read a byte from the referenced stack location and push it onto the stack.

Pseudo Code:

offset = stack[sp - 1]
sp = sp - 1
stack[sp] = stack[top - offset]
sp = sp + 1
pc = pc + 1

Flags Affected:

D	H	C	Z	N

Possible Errors:

tvmStackUnderflow	-	There were not enough bytes in the stack to get the relative index.
tvmStackError	-	The stack index is invalid.

Example:

pushsbx

This operation pops off an index of 3.  Then it gets the third byte from the new top of the stack and pushes it back onto the stack.

Before stack   top 1 0x03 2 0x80 3 0x00 4 0xAA 5 0x32 6 0x02   bottom

After stack   top 1 0xAA 2 0x80 3 0x00 4 0xAA 5 0x32 6 0x02   bottom