Document No. 485HSPR4300 - pg. 1/3
B&B Electronics -- Revised November 2000
This product designed and manufactured in USA of domestic and imported parts by
High Speed (115kb) RS-232 to RS-422/485
Optically Isolated Converter With Surge Suppression
CE
CE
CE
CE
Model 485HSPR
The 485HSPR is a high speed RS-232 to RS-422/485 converter with
optical isolation and surge protection. RS-485 is an enhanced version of the RS-
422 Standard that allows multiple drivers and receivers on a 2 or 4-wire system.
The RS-232 port has a female DB-25 connector with pins 2 (TD), 3 (RD), and 7 (Signal Ground) supported. Pins 4
(RTS) and 20 (DTR) are used to power the RS-232 side of the converter. If your port cannot supply this power, a power
supply may be connected to the RS-232 pins 25 (+12 VDC) and 12 (ground). The RS-485 DB-25 male connector provides
connection for Transmit Data A(-) and B(+), Receive Data A(-) and B(+), and Signal Ground. There is a power jack on the
side of the converter which can be used to power the RS-485 side. A power supply is available from B&B as Part # 485PS.
Power may also be connected through the 485 connector on pins 25 (+12 VDC) and 12 (ground).
Figure 1
JUMPER SELECTION: DRIVER CONTROL
Jumpers JP1, JP3, and JP4 set the method used to control the
RS-422/485 driver. Installing the jumper in position JP1 leaves the driver
constantly enabled. This position should be used for RS-422 operation
and when the 485HSPR will be the master node of a 4 wire RS-485
system.
Jumper position JP3 allows the driver to be directly controlled from
the RS-232 RTS handshake line. The RS-232 device must raise RTS
when transmitting out to the RS-422/485 system. When you are through
transmitting, RTS must be lowered to allow the 485HSPR to receive and
allow other drivers on the line to transmit.
Installing jumper JP4 enables an automatic send data circuit in the
485HSPR that takes care of the control of the RS-422/485 driver. This
circuit senses data on Pin 2 (Transmit Data) of the RS-232 side of the
converter and turns on the RS-422/485 driver. When the data is through
transmitting, the 485HSPR waits one millisecond before shutting of the
RS-422/485 driver. This preset time-out allows continuous transmission of data at 9600 baud or higher. If you need to
change to a baud rate lower than 9600 baud, or would like to configure the 485HSPR for a specific rate, the time-out can
be changed by changing the values of R15 and C9 according to Table 2. If these components need to be changed, you
can remove the surface mount components and install new values in appropriate holes provided on the bottom of the
board. See Figure 1 for the location of R15 and C9.
NOTE: Only 1 of these 3 jumpers can be in place at a time. Which one depends on your configuration.
Table 1 - Jumper Settings
JP1
JP2
JP3
JP4
RS-422 4-Wire Mode
X
RS-485 2-Wire Mode
RTS Control
?
X
Send Data Control
?
X
RS-485 4-Wire Mode
RTS Control
X
Send Data Control
X
X = Jumper in place
? = Remove JP2 to enable echo feature
Document No. 485HSPR4300 - pg. 2/3
B&B Electronics -- Revised November 2000
This product designed and manufactured in USA of domestic and imported parts by
JUMPER SELECTION: RECEIVER CONTROL
The jumper JP2 (echo) determines when the RS-422/485 receiver will be
disabled. Removing this jumper leaves the receiver on at all times. JP2 should be
removed for any four wire setup including RS-422 operation. Putting JP2 on
disables the receiver whenever the driver is turned on. This is useful in two wire
mode when you do not want to see an echo of the data sent from the RS-232
device.
Up to 32 receivers can be driven by any one RS-485 driver, allowing you
to put together large systems with many drop points. If you are using termination
resistors, they should be located at opposite ends of the system.
Figure 3 shows how to interconnect two RS-485 converters in a half-
duplex system using two wires. The resistors Rt is optional, depending on line
length, baud rate, etc. The resistor Rt should be about the impedance of the line
used, which is normally about 120 ohms each.
Proper operation of any RS-485 system requires the presence of a
return path. The RS-485 Standard recommends that a third wire be used for this.
For safety, a 100 ohm, 1/2 watt resistor should be connected between Signal
Ground and the "reference wire" at every drop point. While it may be possible to
interconnect Signal Grounds directly, this is not recommended due to the danger
of circulating currents possibly being present. No wire type or maximum run
length is listed in the RS-485 Standard. However, The RS-422 Standard (which
is very similar) recommends number 24 AWG twisted-pair telephone cable with
shunt capacitance of 16 picofarads per foot, and no more than 4000 feet long.
SPECIFICATIONS:
Data Rate:
Up to 115.2K baud
Connectors:
RS-232 Side:
DB-25 Female (DCE)
RS-422/485:
DB-25 Male (RS-530 Pinouts)
Isolation:
2500VAC Optical Isolation of Data Signals & Ground
Surge Suppression:
7.5V, bi-directional avalanche breakdown device.
500W peak power dissipation.
Clamping time < 1 picosecond (theoretical).
6,000 pF maximum capacitance.
Power Requirements:
RS-232 Side:
Port-powered or 12VDC @ 30ma
RS-422/485:
12VDC @ 100ma
Table 2
COMPONENT REPLACEMENTS
CHANGING BAUD RATE
Baud
Rate
Time
(ms)
Resistor
(R15)
(ohm)
Capacitor
(C9)
(mfd)
300
33.3
330K
0.1
600
16.6
160K
0.1
1200
8.33
820K
0.01
2400
4.16
430K
0.01
4800
2.08
200K
0.01
9600
1.04
100K
0.01
19200
.520
56K
0.01
38400
.260
27K
0.01
57600
.176
16K
.01
115200
.0868
8.2K
.01
DECLARATION OF CONFORMITY
Manufacturer's Name:
B&B Electronics Manufacturing Company
Manufacturer's Address:
P.O. Box 1040
707 Dayton Road
Ottawa, IL 61350 USA
Model Numbers:
485HSPR
Description:
Reversed Optically Isolated
RS-232 to RS-422/485 Converter
Type:
Light industrial ITE equipment
Application of Council Directive:
89/336/EEC
Standards:
EN 50082-1 (IEC 801-2, IEC 801-3, IEC 801-4)
EN 50081-1 (EN 55022, IEC 1000-4-2)
EN 61000 (-4-2, -4-3, -4-4, -4-5, -4-6, -4-8, -4-11)
ENV 50204
EN 55024
Michael J. Fahrion, Director of Engineering
PDF 
ZIP