Download Siemens SIMATIC TIWAY 1 User manual

Run Time Diagnostics
The TI505 NIM monitors itself continuously during normal operation, as follows:
The Operating System continuously performs a ROM integrity test as a background operation.
The NIM periodically verifies that it is capable of communicating with the TI505
A Watchdog Timer circuit in the NIM helps protect against software lockup.
Failures detected in the ROM integrity test will cause the NIM GOOD LED to
extinguish, and force the NIM into a failed state. In this condition the NIM goes to the
Logically Disconnected State (LDS) and will always issue a Disconnect Mode (DM)
response to any commands received.
If the NIM is communicating with the TIWAY network (ON LINE LED is on or flashing)
and fails to communicate with the P/C, it reports this to the host computer with an
Exception Response. Error Code 0A (attached device failed to respond) will be sent, and
the PC GOOD LED will be extinguished. If communication is re-established, the NIM
will return to Normal Response Mode and the PC GOOD LED will illuminate.
The Watchdog Timer circuit helps provide an extra measure of protection against
network lockup due to a failed NIM. This circuit will force a reset if a failure occurs that
prevents the operating software from executing normally. All indicators on the NIM will
be extinguished, and the NIM will not respond to any network commands.
The communication boards include a “jabberstop circuit” which will disable the
transmitter after 4096 state transitions on the line. This prevents a network lockup
should the NIM fail.
TIWAY 1 TI505 NIM User Manual