|Transfer Stack Pointer to X Index
TSX (Transfer Stack Pointer to X Index) transfers the value in the stack pointer to the X index. The reverse of this opcode is TXS.
This pseudo C code shows how the TSX opcode functions when it is executed.
unsigned src = S; // Load the value of the stack pointer as an unsigned byte.
SET_NEGATIVE(src); // Sets the Negative Flag equal to the 7th bit.
SET_ZERO(src); // Sets the Zero Flag if the Operand is $#00, otherwise clears it.
X = (src); // Stores the value of the stack pointer into the X index.