Johnson Controls 300 Series Manual page 64

64 Network Control Module 300 Series Technical Bulletin
N1 Statistics Diagnostics
System representatives have assumed their NCM was faulty due to the
appearance of error counts during the N1 Statistics Diagnostics. See
the Using Diagnostics chapter (LIT-120159) of the Operator
Workstation User's Manual. Some error counts are typically generated
when running the diagnostics. Determining when the normal range of
errors has been exceeded is somewhat difficult because of site and
configuration variables.
If, when running the diagnostics, you believe there is an excessive
number of errors, regard the errors as a warning to test the
functionality of the NCM. Assume that a properly functioning NCM is
good, and there is no need to return it. A rule of thumb is that NCMs
typically keep diagnostic errors around 0.1% or less.
Remember, in situations where diagnostic errors are greater than 0.1%,
there can be causes other than the NCM. If the errors increase as fast
as the number of transmits and receives process, something is likely
wrong.
N1 End-of-Line Termination Notes
Keep the following items in mind for N1 End-of-Line Termination:
• Use 93-ohm terminators and RG-62 type cable for the ARCNET
N1 LAN. Do not use RG-62 type cable for Ethernet networks.
• The OWS ARCNET card may contain an internal EOL termination
resistor.
- To prevent adding a third resistor to the network, determine
whether your OWS ARCNET card has an internal EOL
resistor. Refer to your ARCNET card manual.
- If the ARCNET card has an internal resistor, make sure that it
is removed or disabled. Refer to your ARCNET card manual.
Ensure this either by positioning the OWS at the end of the
line, or jumper the board to disengage the EOL resistor, and
adding a resistor at the proper position.
- Always use an External 93-ohm terminator and a coax tee
connector to terminate at the end of the lines.
Notes: On the approved active hubs, the cables are terminated
internally. On the approved active links, external terminators are
required for each EOL connection.