CANOGA PERKINS 2340 Universal Fiber Optic Modem - Manual (Page 19)

EdgeAccess® Universal Chassis System
Model 2340 Model User Manual 3-5
3.3 L131: EIA-422, DC-37 With Control Signals
The L131 ELIM for EIA-449 is electrically compatible with the EIA-422 specifications for clock and
data and with EIA-423 for control signals. It uses a female DC-37 connector; Table 3 lists the pinout.
SD, RD, ST, RT and TT provide the primary data and clock signals. ST provides the transmit clock
reference for Internal and Slave modes. RT provides the clock for the received data. TT provides the
transmit clock for External mode.
The control signal outputs are unbalanced drivers and the B-leads of the differential control signal
outputs are tied to signal ground to comply with EIA-422. None of the control leads interact with the
data transmission, but they do comply with DTE interface requirements. Most of the control leads are
end-to-end signal channels that can conform to EIA-449 interface standards.
The EIA-449 interface includes three end-to-end control leads; input to output:
• RS to RR
• TR to IC
• NS to SQ
DM and TM provide local status and follow the RS-449 functions. DM typically indicates that the
modem is ready to receive data. LL and RL are loopback control inputs and follow the software
setting, unless a 2340 in a Model 1040 is in hardware mode and the function switch on the enclosure
is set for loopback, then LL and RL are ignored. For details on the software and loopback tests, see
Sections 4.12 and 5.1.
Table 3. EIA-449 Interface DC-37 Pin Assignments
DC-37 Pin EIA-449 Signal Function Direction
1 SHLD Shield (Ground)
3/21 not used
4/22 SD Send Data In
5/23 ST Send Timing Out
6/24 RD Receive Data Out
7/25 RS Request to Send In
8/26 RT Receive Timing Out
9/27 CS Clear to Send Out
10 LL Local Loopback In
11/29 DM Data Mode Out
12/30 TR Terminal Ready In
13/31 RR Receiver Ready Out
14 RL Remote Loopback In
15 IC Incoming Call Control
17/35 TT Terminal Timing In