Connectors
The RMC SERIAL's 9-pin male DB connector is used for RS-232 communications. This requires a 9-pin female connector on the RMC SERIAL end of the connecting cable. The other end of the cable must match the master/host hardware, which may be a 9-pin, 25-pin, RJ-11, connector block, or other connector.
See also General Wiring Information.
The following diagram shows the pin assignments on the RS-232 9-pin connector:
RMC Male DB9 Pin-out:
|
Pin # |
RS-232 Function |
|
1 |
DCD - Not used by RMC |
|
2 |
RxD - Receive Data |
|
3 |
TxD - Transmit Data |
|
4 |
DTR - Not used by RMC |
|
5 |
GND - Common |
|
6 |
DSR - Not used by RMC |
|
7 |
RTS - Ready To Send |
|
8 |
CTS - Clear To Send |
|
9 |
Not Connected |
Cabling
A null-modem or crossover cable is typically used for RS-232 communications. See the following wiring diagram for details.
Note: The RTS and CTS lines are only required if Hardware (RTS/CTS) flow control is selected in the RMC SERIAL configuration.
The RMC RS-232 communications require only three conductors in the cable: RxD, TxD, and GND. A five-conductor cable must be used if the CTS and RTS signals are used.
Delta recommends that a shielded cable be used to limit susceptibility to outside electrical interference.
Cable Length
One of the characteristics that limit the length of an RS-232 cable is capacitance. Most cables have a capacitance rating in pF/ft. The maximum distance that you can reliably transmit signals can be determined by answering a few questions and plugging the answers into the following formula:
MaxLength = 2400 pF / ( C + ( Shield * C ) )
Where: Shield = 2 for shielded cable and 0.5 for unshielded cable
C is the capacitance rating of the cable in pF/length
2400 pF is derived by taking the maximum capacitance specified by ANSI/TIA/EIA-232-F (2500 pF) and subtracting 100 pF for the input capacitance of the receiver
If you need to run your communications farther than allowed by this formula, then you must either use a cable with lower capacitance or use RS-422 or RS-485.
Example:
The cable that is being used is shielded and has a capacitance of 15 pF/ft.
MaxLength = 2400 pF / ( 15 pF/ft + (2 * 15 pF/ft) )
= 2400 pF / ( 45 pF/ft )
= 53.3 ft
Copyright (c) 1997-2015 by Delta Computer Systems, Inc.