User`s manual

CHAPTER 5
RS-232C/422/485 INTERFACING
5-2
DTE vs. DCE
The ESTeem is configured as a Data Communication
Equipment (DCE) device. The following signals
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 directly connected.
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.
FLOW CONTROL
The ESTeem can be enabled to support SOFTWARE or
HARDWARE flow control.
Software Flow Control
Software flow control is enabled by the XSFLOW
(on/off) command in the ESTeem. When XSFLOW is
ON the ESTeem will respond to <XOFF>, (stop) and
<XON>, (off) commands from the RS-232 port. The
factory default setting is ON. The default value for
START is 17 (CTRL Q) and for STOP is 19 (CTRL S).
Hardware Flow Control
Hardware flow control is enabled by the XHFLOW
(on/off) command in the ESTeem. The factory default
value is OFF.
When XHFLOW is enabled (on) the control signal lines,
Request To Send (RTS, pin 4), Data Carrier Detect
(DCD, pin 8), and Clear To Send (CTS, pin 5) are
available to the user at the RS-232C connector. The CTS
and RTS signals are used to control the flow of data into
and out of the ESTeem.
The CTS signal on pin 5 is used to control the data into
the ESTeem. When CTS is set (high on pin 5) the
modem is ready to receive data. When CTS is reset (low
on pin 5) the ESTeem is not ready to receive data.
The RTS signal is used to control data out of the
ESTeem. RTS is set (high on pin 4), by the user to
indicate to the ESTeem that the user is ready to receive
data. When reset, the user is not ready to receive data.
(NOTE: Low = On, High = Off).