Siemens SIMATIC TIWAY 1 - Manual (Page 156)

HOST COMMAND SET REFERENCE
UNILINK HOST ADAPTER 5–71
USER MANUAL
5.7.4 Reset Adapter — FF
The RESET ADAPTER command forces the UNILINK Host Adapter to execute
a hardware reset. The reset will begin within one second after the response has
been returned to the host computer. Your applications software should allow a
minimum of 2–3 seconds for the reset to complete.
Command: FF
Response: FF