Service manual

98
Installation & Service Manual
Appendix B - Hardware Specifications and Cabling
Cyclades-TS
RS-232
Signal
Name/Function
(Input/Output)
DB-25 pins
(Standard)
DB-9 pins
(Standard)
RJ-45 pins
(Cyclades)
Chassis Safety Ground 1 Shell Shell
TxD Transmit Data (O) 2 3 3
RxD Receive Data (I) 3 2 6
DTR Data Terminal Ready (O) 20 4 2
DSR Data Set Ready (I) 6 6 8
DCD Data Carrier Detect (I) 8 1 7
RTS Request To Send (O) 4 7 1
CTS Clear To Send (I) 5 8 5
Gnd Signal Ground 7 5 4
Straight-Through vs. Crossover Cables
The RS-232 interface was originally intended to connect a DTE (computer, printer and other serial devices) to a
DCE (modem) using a straight-through cable (all signals on one side connecting to the corresponding signals
on the other side one-to-one). By using some “cabling tricks”, we can use RS-232 to connect two DTEs as is
the case in most modern applications.
A crossover (a.k.a. null-modem) cable is used to connect two DTEs directly, without modems or communication
lines in between. The data signals between the two sides are transmitted and received and there are many
variations on how the other control signals are wired. A “complete” crossover cable would connect TxD with
RxD, DTR with DCD/DSR, and RTS with CTS on both sides. A “simplified” crossover cable would cross TxD
and RxD and locally short-circuit DTR with DCD/DSR and RTS with CTS.
Which Cable Should be Used
First, look up the proper cable for your application in the table below. Next, purchase standard off-the-shelf
cables from a computer store or cable vendor. For custom cables, refer to the cable diagrams to build your own
cables or order them from Cyclades or a cable vendor.