Verilink AS100 (896-502379-001) Product Manual - Manual (Page 39)

Configuration Parameters
Access System Centum Series User Manual 3-15
requires special user cabling and a very specific DCE configuration.
Please refer to Appendi xC, Special Serial Port Cabling for more
information.
Int/Ext should be used for Serial Port #1 if the attached user DTE is
substantially far away from Centum Series and/or if Serial Port #1 is
to be used as the system’s master clock. See Timing Source (item
#12, above).
Int/Ext should be used for Serial Port #2 if the attached user DTE is
substantially far away from the Centum unit. The Centum unit will
provide RX-clock to the attached DTE and will accept TX-clock
from the DTE.
The Int/Ext setting requires a special DTE requires a special DTE
configuration or a modified cable. Please refer to Appen d ixC,
Special Serial Port Cabling for more information.
Important Notes:
a. If Int/Ext timing has been selected for Serial Port #1 because
Serial Port #1 is to be used as the system’s master clock (see
item #12, above), the recommendation in Appendi xC must be
followed.
b. If excessive DTE cable distance is the only concern, consider the
following:
• Clocking problems appear as periodic (predictable) error
bursts.
• Internal Serial Port timing should first be attempted with a
normal DTE configuration and a standard cable.
• If clocking problems occur, they can frequently be corrected
by using clock inversion (items #17 and #24, above) and
retaining the normal DTE configuration and the standard
cable.