How does the Siemens S5 PLC communicate with the PC?

PC-TTY cable S5 PLC total clear
Two methods of performing total clearing:
1. Turn the reset setting switch to the OR position and turn the RN/ST switch RN-ST-RN-ST-RN
2. Execute the PLC’s Delete with the programmer. The operation is:
Object –> Blocks –> Delete –> in the PLC,
Select all blocks=overall reset, then execute Delete
Note: It is necessary to set the RN/ST switch to the ST position for total clearance.
During the execution of the PLC, the CPU’s BASP light is on, and the rest of the CPU (including the ST light) is off.
Clear the following after the total clearing:
PLC program memory
2. All data (PII PIQ F T C RS )
3. All errors (estimated to be RS information)