B&B Electronics FOSTCDRI-INV - Quick Start Guide - Manual (Page 2)

Troubleshooting
When using Point to Point mode can I set one
of the FOSTCDRi’s as 232 and the other as 422
or 485?
Yes.
What do the TX Bias and RX Bias switches do?
They put biasing in or out of the circuit. There is a 1.2k ohm resistor
across the transmit pair and the receive pair.
(Applies to RS-422/485 only)
BIASING
Please review our biasing tech note on our 422/485
application guide.
CONNECTING A SIGNAL GROUND
(COMMON, REFERENCE) ON THE RS-422/485 SIDE
The specifications for most RS-422 and RS-485 devices indicate that
the device can withstand a maximum VCM of -7 volts to +12 volts.
The function of the GND connection is to tie the signal grounds of all
nodes on a network to one common ground potential. This ensures
that the common mode voltage cannot exceed the specified value.
A signal ground is required on the FOSTCDRi because it is an
optically isolated device. If you do not have a signal ground
(common, reference) on your RS-422/485 device you can connect
to the DC power ground of your RS-422/485 device.
Caution: Be sure that this is connected correctly.
The FOSTCDRi has the fiber optic transmit light ON in the idle state.
If you require the fiber optic transmit light OFF in the idle state you
can order the FOSTCDRi-INV. (The FOSTCDRi and the FOSTCDRi-INV
will not work together.)
What is the difference between the FOSTCDRi
and the FOSTCDRi-INV?
On the FOSTCDRi we keep the light in the fiber turned on when no
data is transmitted and the input signal is in the MARK state (idle).
If light is lost or too low, the electrical signals go to the SPACE state.
The input signal turns the light Off/On in step with the data. This
model has no indicator for Transmit or Receive, if no light is received,
the RD output will be positive relative to GND (normally negative),
and in RS-422 or RS-485 mode, no light will set the TD(A)- line
high relative to TD(B)+. The usual voltage with light in the fiber and
no signal sets the B line high relative to A (about 4.4 Volts DC no
termination). To check, connect a fiber patch cable from the TX
connector into the RX connector.
The FOSTCDRi-INV is the opposite. The fiber is off in the idle state.
Document number – pn8953_r002_FOSTCDRi-x_1312qsg
© 2012 B&B Electronics Manufacturing Company
1-888-948-2248 | Europe: +353 91 792444
www.bb-elec.com
Recommended Accessories
and Power Supplies
Fiber Optic Cable
35mm DIN Rail to Panel
Mount Bracket
DFMM-STST-1M
DRPM25
707 Dayton Road | PO Box 1040 | Ottawa, IL 61350
Phone: 815-433-5100 | Fax: 815-433-5109
www.bb-elec.com | E-mail: [email protected]
http://www.bb-elec.com/FOSTCDRi
Fast and easy on the web: www.bb-elec.com
FOSTCDRi Fiber Converter
Additional items required but not included:
10 - 48 VDC Power Supply
Serial Cable
Muli-mode Fiber Optic Cable with
ST Connectors (62.5/125 micro-meter)
First Things First...
Before you begin, be sure you have
the following:
Industrial Serial to Multi-mode Fiber Converters
FOSTCDRi & FOSTCDRi-INV
http://www.bb-elec.com/FOSTCDRi/
ACC
http://www.bb-elec.com/FOSTCDRi/
ACC
Industrial Power Supply
MDR-20-24
http://www.bb-elec.com/FOSTCDRi/
ACC
Fast, Easy Answers
• First, check step 6.
• Then use your smart
phone to access complete
documentation on our
web site. Simply scan
the code to the right.