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USER
MANUAL
MODEL 285
and 285S
RS-232 to RS-485
Interface Converters
SALES OFFICE
(301) 975-1000
TECHNICAL SUPPORT
(301) 975-1007
http://www.patton.com
Part# 07M285-B
Doc# 047012UB
Revised 9/29/93
Revision C and above
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1.0 WARRANTY INFORMATION
Patton Electronics warrants all Model 285 components to be free
from defects, and will—at our option—repair or replace the product
should it fail within one year from the first date of shipment.
This warranty is limited to defects in workmanship or materials,
and does not cover customer damage, abuse, or unauthorized modification. If this product fails or does not perform as warranted, your sole
recourse shall be repair or replacement as described above. Under no
condition shall Patton Electronics be liable for any damages incurred
by the use of this product. These damages include, but are not limited
to, the following: lost profits, lost savings, and incidental or consequential damages arising from the use of or inability to use this product. Patton Electronics specifically disclaims all other warranties,
expressed or implied, and the installation or use of this product shall
be deemed an acceptance of these terms by the user.
1.1 RADIO AND TV INTERFERENCE
The Model 285 generates and uses radio frequency energy, and if
not installed and used properly—that is, in strict accordance with the
manufacturer's instructions—may cause interference to radio and television reception. The Model 285 has been tested and found to comply
with the limits for a Class A computing device in accordance with the
specifications in Subpart J of Part 15 of FCC rules, which are designed
to provide reasonable protection from such interference in a commercial installation. However, there is no guarantee that interference will
not occur in a particular installation. If the Model 285 does cause interference to radio or television reception, which can be determined by
disconnecting the RS-232 interface, the user is encouraged to try to
correct the interference by one or more of the following measures:
moving the computing equipment away from the receiver, re-orienting
the receiving antenna, and/or plugging the receiving equipment into a
different AC outlet (such that the computing equipment and receiver
are on different branches).
1.2 SERVICE
All warranty and non-warranty repairs must be returned freight
prepaid and insured to Patton Electronics. All returns must have a
Return Materials Authorization number on the outside of the shipping
container. This number may be obtained from Patton Electronics
Technical Service at (301) 975-1007.
Packages received without an
RMA number will not be accepted.
Patton Electronics' technical staff is also available to answer any
questions that might arise concerning the installation or use of your
Model 285. Technical Service hours: 8AM to 5PM EST, Monday
through Friday.
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2.0 GENERAL INFORMATION
Thank you for your purchase of this Patton Electronics product.
This product has been thoroughly inspected and tested and is warranted for One Year parts and labor. If any questions or problems arise
during installation or use of this product, please do not hesitate to contact Patton Electronics Technical Support at (301) 975-1007.
2.1 FEATURES
• Bi-directionally converts RS-232 signals to balanced RS-485
• Supports up to 50 multipoint device drops in a polling environment
• Supports data rates to 115.2 Kbps on 2 or 4 wires
• Passes transmit & receive data, one control signal each direction
• DTE/DCE switch selectable on RS-232 interface
• Interface powered—no AC power or batteries are required
• Variable high/low impedancesettings
• Carrier can be set as "constantly on" or "controlled by RTS"
2.2 DESCRIPTION
Communicate between RS-485 devices and RS-232C using the
Patton Electronics Model 285 Interface Converter. The Model 285
converts RS-232C signals into balanced RS-485 signals over one or
two twisted pair. Drawing all necessary operating power from the
RS-232 interface, the Model 285 needs no AC power or batteries.
The Model 285 has six convenient configuration switches to adapt
the unit for DCE or DTE, 2 or 4 wire, full or half duplex, and point-topoint or multi-point applications. The Model 285 will support up to 50
polled devices without distance degradation.
The surge protected Model 285S uses high speed avalanche
diodes to clamp voltage surges caused by lightning, motors, switches,
etc. With surge handling capacity of 600W per wire at 1mS, the 285S
has the ability to protect itself and connected equipment from common
damaging surges.
Connector options to the RS-485 are via DB-25 (employing the
RS-530 interface), RJ-11, RJ-45, or terminal blocks with strain relief.
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3.0 CONFIGURATION
The Model 285 is configured using six PC board mounted switches. Figure 1 (below) shows the switch locations, along with the location of the terminal blocks and optional surge protectors:
3.1 SETTING THE DTE/DCE SWITCH
For your convenience, the Model 285 has an externally accessible DTE/DCE switch (see Figure 2, below). If the device connected to
the Model 285 is a modem or multiplexer (or is wired like one), set the
switch to "DTE". This setting causes the Model 285 to behave like
Data Terminal Equipment and transmit data on pin 2.
If the device connected to the Model 285 is a PC, terminal or host
computer (or is wired like one), set the switch to "DCE". This setting
causes the Model 285 to behave like Data Communications Equipment
and transmit data on pin 3.
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3.2 SETTING CONFIGURATION SWITCHES SW1 AND SW2
The five switches shown in Figure 3 (below) configure the Model
285 for RTS/CTS delay, echo, method of carrier control, impedance,
and 2-wire/4-wire operation. These switches are located
internally
on
the Model 285's PC board. To access SW1 and SW2, use a small flat
blade screw driver to pop open the Model 285's case as shown in
Figure 4 (below):
4
DCE/DTE
Switch
2-wire/4-wire
Switch
Surge
Suppressors
(285S only)
Terminal
Block
Control
Switches
"ON"
"OFF"
SW2SW1
Figure 1. Model 285 board, showing switch locations
Figure 2. Close up of external DCE/DTE switch
Figure 3. Close up of switches SW1 and SW2 on the PC board
Figure 4. Opening the Model 285's plastic case with a small screw driver
DCE DTE
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3.2.1 CONFIGURATION SWITCH FUNCTIONS
The table and descriptions below detail the functions of the five
configuration switches. Read this information carefully before setting
the switches.
SW1-1: RTS/CTS Delay: Switch 1-1 determines how long circuit CB (CTS) takes to become active after RTS is asserted (DCE
Mode only). RTS delay of 8 mSec will give any signal from any other
device time to clear the transmit line. In DTE mode, CTS is open.
SW1-2: Echo Enable: With Switch 1-2 in the ON position, the
285 echoes transmitted data back to the transmitting device. This is
so the user can see what is being transmitting to the remote device.
(Typically used in half duplex modes only).
SW1-3: Carrier: With Switch 1-3 in the ON position, the 285
transmitter operation follows circuit CA (Request to Send). When RTS
is low, the 285 transmitter operation is off (0V) (DCE mode only).
SW1-4: Impedance: Switch 1-4 defines a termination resistance.The 285 transmitter can drive 50 unit loads including two terminationresistances of 120 Ohms each.
SW2: 2 Wire/ 4 Wire: Switch 2 determines 2 wire (half duplex)
or 4 wire operation.
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3.2.2 CONFIGURATION SWITCH APPLICATIONS
The table below shows you how to set the Model 285's configuration switches to fit several common applications. If you have any
questions about the proper settings for your application, call Patton
Technical Support at (301) 975-1007.
*NOTE: RTS/CTS Delay (SW1-1) setting should be based upon transmission timing.
3.2.3 WHEN YOU'RE FINISHED CONFIGURING...
Once you've finished setting the Model 285's configuration
switches,
pause
before you snap the case halves back together. If you
are connecting the RS-485 interface using the internal terminal blocks,
go to Section 4.1.3 and continue the installation procedure. If you are
connecting the RS-485 interface using RS-11, RS-45 or DB-25, go
ahead and snap the case halves back together now (don't force a fit—
make sure all the pieces are properly set before snapping the case
halves shut).
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RTS/CTS (SW1-1)* ON ON ON ON ON
Echo (SW1-2) OFF ON OFF ON OFF
Carrier (SW1-3) OFF ON ON Master-OFF ON
Slaves-ON
Impedance (SW1-4) ON ON ON Master - ON
Slaves - HIGH
Last Slave - ON
2wire/4wire (SW2) ON ON OFF ON OFF
TYPICAL SWITCH APPLICATIONS
Point-to-Point
Switch
Settings
Multi-point
4W 2W 4W 2W4W HDX
SWITCH SUMMARY TABLE
Position Function Off Position On Position
SW1-1 RTS/CTS Delay 0 mSec 8 mSec
SW1-2 Echo Enable Echo "Off" Echo "On"
SW1-3 Carrier Control Constantly "On" Controlled by RTS
SW1-4 Impedance High (120K Ohm) Low (120 Ohm)
SW2 2 wire/4 wire 2-wire 4-wire
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4.1.2 4-WIRE CONNECTION USING RJ-11 OR RJ-45
The RJ-11 and RJ-45 connectors on the Model 285's RS-485 side
are pre-wired for a standard TELCO wiring environment. The
signal/pin relationships are shown below:
RJ-1
1 SIGNAL RJ-45 SIGNAL
1...................GND* 1 .................N/C
2...................RCV- 2 .................GND*
3...................XMT+ 3 .................RCV-
4...................XMT- 4 .................XMT+
5...................RCV+ 5 .................XMT-
6...................GND 6 .................RCV+
7 .................GND
8 .................N/C
In most modular RS-485 applications it is necessary to use a
"cross over" cable. The diagram below shows how a cross over cable
should be constructed for an environment where both the Model 285
and the RS-485 device use a 6-wire RJ-11 connector. Similar logic
should be followed when using RJ-45 connectors or a combination of
the two.
MODEL 285 RS-485 DEVICE
SIGNAL
PIN# PIN# 422 SIGNAL
GND* 1
RCV- 2 .........................4 XMT-
XMT+ 3 .........................5 RCV+
XMT- 4 .........................2 RCV-
RCV+ 5 .........................3 XMT+
GND 6
*Connection to ground is optional
**Standard AT&T pin assignements - yours may be different.
4.0 INSTALLATION
Once you have properly set the configuration switches, you are
ready to connect the Model 285 to your system. This section tells you
how to properly connect the Model 285 to the RS-485 and RS-232
interfaces, and how to operate the Model 285.
4.1 CONNECTION TO THE RS-485 INTERFACE
To function properly, the Model 285
must
have one or two twisted
pairs of metallic wire. These pairs must be "dry" (unconditioned)
metallic wire, between 19 and 26 AWG (the higher number gauges
may limit distance somewhat).
For your convenience, the Model 285 is available with several different physical interfaces on the RS-485 side: DB-25 (following the
RS-520 standard), RJ-11 jack, RJ-45 jack, and terminal blocks with
strain relief.
4.1.1 4-WIRE CONNECTION USING THE DB-25
The DB-25 connector on the Model 285's RS-485 side conforms to
the RS-530 interface standard. When connecting to an RS-485
device that also conforms to the RS-530 standard, your cable should
be "crossed over" in the manner shown below:
MODEL 285 RS-485 (530) DEVICE
SIGNAL
DB-25 PIN DB-25 PIN SIGNAL
XMT+ 2...........................3 RCV+
XMT- 14...........................16 RCV-
RCV+ 3...........................2 XMT+
RCV- 16...........................14 XMT-
NOTE: It is not necessary that the RS-485 device adhere to the RS-530 standard. However, you must make sure that the signals, polarities, and pairing of
your connection conform to the above diagram.
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1
2
3
4
5
6
1
2
3
4
5
6
7
8
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4.1.3 4-WIRE CONNECTION USING TERMINAL BLOCKS
If your RS-485 application requires you to connect two pairs of
bare wires to the Model 285, you will need to open the case to access
the terminal blocks. The following instructions will tell you how to open
the case, connect the bare wires to the terminal blocks, and fasten the
strain relief collar in place so that the wires won't pull loose.
1. You should already have the case open for the configuration
procedure. If not, open the case according to the diagram in Section
3.2.
2. Strip the outer insulation from the twisted pairs about one inch
from the end.
3. Strip back the insulation on each of the 2 twisted pair wires
about .25".
4. Connect
one pair
of wires to XMT+ and XMT- (transmit positive
and negative) on the terminal block, making careful note of which color
is positive, and which color is negative.
5. Connect the
other pair
of wires to RCV+ and RCV- (receive
positive and negative) on the terminal block, again making careful note
of which color is positive, and which color is negative.
Ultimately, you will want to construct a two pair cross over cable
that makes a connection with the RS-485 device as shown below:
Model
285 RS-485 Device
XMT+.............................RCV+
XMT-..............................RCV-
RCV+.............................XMT+
RCV-..............................XMT-
6. If there is a shield around the telephone cable, it may be connected to "G" on the terminal block. We recommend connecting the
shield at the computer end only to avoid ground loops. A ground wire
is
not necessary
for proper operation of the Model 285.
7. When you finish connecting the wires to the terminal block, the
assembly should resemble the diagram below:
8. Place the 2 halves of the strain relief assembly on either side
of the telephone wire and press together very lightly. Slide the assembly so that it is about 2 inches from the terminal posts and press
together firmly. If your cable diameter is too small or too large for our
strain relief, please contact our technical support. We have strain relief
assemblies to accommodate most cable diameters.
(continued)
+RCV- G -XMT+
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+RCV- G -XMT+
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9. Insert the strain relief assembly with the wire going through it
into the slot in the bottom half of the modem case and set it into the
recess in the case.
10. BEND the top half of the case as necessary to place it over
the strain relief assembly. Do not snap the case together yet.
11. Insert one captive screw through a saddle washer and then
insert the captive screw with the washer on it, through the hole in the
DB-25 end of the case. Snap that side of the case closed. Repeat the
process for the other side. This completes the cable installation
process.
4.1.4 2-WIRE CONNECTION
Most RS-485 devices employ a two-wire, half duplex configuration.
When using this configuration, be sure to first set the Model 285 to
"two wire" mode—then use
only the transmit (XMT) pair
as shown
below:
285
SIGNAL RS-485 SIGNAL
XMT+....................................+
XMT- .....................................-
The above wiring pattern applies regardless of whether you are
making the RS-485 connection via DB-25, RJ-11, RJ-45 or terminal
blocks. For specific wiring instructions, please refer to the previous
pages of Section 4.
4.2 CONNECTION TO THE RS-232 INTERFACE
Once you have properly configured the Model 285 and connected
the twisted pair wires correctly, all that remains is to plug the 285
directly into the DB-25 port of the RS-232 device. After doing so,
remember to insert and tighten the two captive connector screws.
(Note: If you must use a cable to connect the Model 285 to the RS-232
device, make sure it is a
straight through
cable of the shortest possible
length—we recommend 6 feet or less).
4.3 OPERATING THE MODEL 285
Once the Model 285 is properly installed, it should operate transparently—as if it were a standard cable connection. Operating power
is derived from the RS-232 data and control signals; there is no
"ON/OFF" switch. All data signals from the RS-232 and RS-485 interfaces are passed straight through. Additionally, one hardware flow
control signal is passed
in each direction
.
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APPENDIX A
SPECIFICATIONS
Transmission Format: Asynchronous
Data Rate: Up to 115,200 bps
Transmit Line: 2, 4 wire unconditioned twisted pair
Transmit Mode: Full or half duplex
Transmit Level: 0 dBm
Range: Up to 9 miles
Control Signals: DSR turns "ON" immediately after the terminal
raises DTR; DCD turns "ON" after recognizing the
receive signal from the line; CTS turns on after
the terminal raises RTS
Carrier: The carrier is strap selected either continuous operation or
switched operation, controlled by RTS
Surge Protection: 600W power dissipation at 1 mS and response
time less than 1.0 pS
Power: None required, uses ultra low power from EIA data and con
trol signals
Size: 2.66" x 2.10" x 0.73"
APPENDIX B
RS-232C PIN CONFIGURATIONS
13 14
1- (FG) Frame Ground
2- (TD) Transmit Data To Model 285
3- (RD) Receive Data From Model 285
4- (RTS) Request to Send To Model 285
5- (CTS) Clear to Send From Model 285
6- (DSR) Data Set Ready From Model 285
7- (SG) Signal Ground
8- (DCD) Data Carrier Detect From Model 285
To Model 285 Data Term. Ready (DTR) - 20
DIRECTION STANDARD "DCE" SETTING DIRECTION
1- (FG) Frame Ground
2- (TD) Transmit Data From Model 285
3- (RD) Receive Data To Model 285
4- (RTS) Request to Send From Model 285
5- (CTS) Clear to Send To Model 285
6- (DSR) Data Set Ready To Model 285
7- (SG) Signal Ground
8- (DCD) Data Carrier Detect To Model 285
From Model 285 Data Term. Ready (DTR) - 20
DIRECTION STANDARD "DTE" SETTING DIRECTION
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APPENDIX C
BLOCK DIAGRAM
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