CANOGA PERKINS 2340 Universal Fiber Optic Modem - Manual (Page 22)

Model 2340 Model User Manual 3-8
3.7 L138: EIA-422, DC-37 Without Control Signals
The L138 ELIM is electrically compatible with the EIA-422A specifications. It includes a female
DC-37 connector, but not the control signals available with the EIA-449 interface. Table 9 lists the
supported clock and data signals.
Table 9. EIA-422, Without Control Signals, DC-37 Pin Assignments
Pin Signal Name Direction
15/33 RDA/B Receive Data Out
17/35 SCRA/B Receive Clock Out
9/27 TDA/B Transmit Data In
5/23 SCTEA/B Terminal Timing In
3/21 SCTA/B Transmit Clock Out
19 FG Frame Ground
1 SG Signal Ground
3.8 L139: T88
The L139 ELIM is electrically compatible with Mil-Std 188-114C; it supports only the clock and
data. It includes five TwinAx connectors. Table 10 lists the supported signals.
Table 10. EIA-422 Interface TwinAx Signals
Signal Name Direction
SCR Receive Clock Out
RXD Receive Data Out
TXD Transmit Data In
SCTE External Transmit Clock In
SCT Transmit Clock Out
3.9 Operating Modes and Transmit/Receive Timing
The 2340 operates in a variety of modes that support different sources of the timing signals; you can
set these on the Functional Configuration screen. For details on the Functional Configuration screen
and configuring the parameters for various interfaces, see Section 4.7.
The TD Timing signal is the clock that sends data to the fiber interface. It can be either the SCT or
SCTE signals. Use SCT Inverted to allow for data delays in relation to the clock and prevent bit
errors. Use SCTE Sampled if the clock is gapped.
The RD Timing signal is the clock that shifts data from the modem to the electrical interface. It can
be either the SCT or SCR signals.