Siemens 500 NIM - Manual (Page 50)

Installation 3-15 SIMATIC TIWAY I Series 500 NIM User Manual
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.
Once the NIM has reached the Normal Operating Mode and fails to
communicate with the controller, 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/NIM COMM GOOD LED will be extinguished. If
communication is re-established, the NIM will return to Normal Mode and
the PC/NIM COMM GOOD LED will illuminate.
The Watchdog Timer circuit provides 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.
The User-Initiated Self-Test performs a complete test of the NIM hardware,
including the communication ports. Test execution is detailed in the
following paragraphs.
!
CAUTION
Since this test includes the communication ports, be sure to disconnect the NIM
from the TIWAY I network.
Failure to disconnect the NIM from the TIWAY I network could cause unpredictable
process operation during the user-initiated self-test.
1. Disconnect network cables from both network ports of the NIM.
2. Install loopback connectors on the RS-232-C port(s) of the NIM.
3. Make certain the Local/Remote switch is in the “Local” position.
4. Press the reset switch.
5. Press the self-test switch.
User-Initiated
Self-Test