User Manual Part 1

CHAPTER 5
RS-232C/422/485 INTERFACING
Revised: 8 Oct 03 5-1 EST P/N AA104
DTE vs. DCE
The ESTeem is configured as a Data Communication Equipment (DCE) device. The following signals are available at the
RS-232C connector located at the rear of the unit.
Pin Description
---------------------------------------------------------------------
1 FG Shield Ground
2 TXD Transmit Data (Input)
3 RXD Receive Data (Output)
DCE 4 RTS Request To Send (Input)
5 CTS Clear to Send (Output)
7 SG Signal Ground
8 DCD Data Carrier Detect (Output)
12 RTS Request To Send (Output)
20 DTR Data Terminal Ready (Input)
22 Ring Ring Indicator (Output)
The important thing to remember is that for the ESTeem to communicate with an external device, the data output from pin 3 of
the ESTeem RS-232C connector must be connected to the data input of the device you are connected to; otherwise, the ESTeem
won't work. Likewise, the data input to pin 2 of the ESTeem must be connected to the data output of the device you are
connected to. Normally, if the equipment you are connecting to looks like a terminal or computer (DTE), its input, Receive Data
(RXD), will be on pin 3 its output, Transmit Data (TXD), will be on pin 2. Therefore, the ESTeem can be connected directly.
If the device you are connecting to is configured as a modem (DCE), its output will be on pin 3. If this configuration is
connected to the ESTeem, damage may result to the ESTeem or the connecting device. In this case, you can purchase a null
connector that internally reverses pins 2 and 3.
Whatever your situation may be, it is always best to check the manual on your particular device and connect accordingly.
Purchase or fabricate a RS-232C shielded cable for your ESTeem. The ESTeem requires a standard male 25 pin D connector on
one end of the cable for proper connection.
Remember to install the small retaining screws on either side of the cable connector. Tightening these screws keeps you from
accidentally losing connection with your ESTeem.
Notes:
• The ESTeem requires a shielded RS-232 cable. This is to prevent unwanted electrical noise from entering the ESTeem
and also to prevent any electrical noise from getting out of the ESTeem.
• Remember -- always use a shielded RS-232C cable.
• Pins 9, 10, 14, & 16 are used for RS-422/485 interfacing and should be left open if not used.