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Appendix C - Electrical Interface 

OMG-USB-SER-2

 

Page 

13

 

 

RS-485 

RS-485 is backwardly compatible with RS-422; however, it is optimized for 
partyline or multi-drop applications. The output of the RS-422/485 driver is 
capable of being 

Active

 (enabled) or 

Tri-State

 (disabled). This capability allows 

multiple ports to be connected in a multi-drop bus and selectively polled. RS-485 
allows cable lengths up to 4000 feet and data rates up to 10 Megabits per second. 
The signal levels for RS-485 are the same as those defined by RS-422. RS-485 has 
electrical characteristics that allow for 32 drivers and 32 receivers to be 
connected to one line. This interface is ideal for multi-drop or network 
environments. RS-485 tri-state driver (not dual-state) will allow the electrical 
presence of the driver to be removed from the line. Only one driver may be active 
at a time and the other driver(s) must be tri-stated. RS-485 can be cabled in two 
ways, two wire and four wire mode. Two wire mode does not allow for full duplex 
communication and requires that data be transferred in only one direction at a 
time. For half-duplex operation, the two transmit pins should be connected to the 
two receive pins (Tx+ to Rx+ and Tx- to Rx-). Four wire mode allows full duplex 
data transfers. RS-485 does not define a connector pin-out or a set of modem 
control signals. RS-485 does not define a physical connector. 

 

Summary of Contents for OMG-USB-SER-2

Page 1: ...www omega com e mail info omega com User sGuide OMG USB SER 2 Two Port RS 232 422 485 to USB Adaptor Shop online at...

Page 2: ...TCH EXAMPLES CONTINUED 7 TECHNICAL DESCRIPTION 8 FEATURES 8 CONNECTOR PIN ASSIGNMENTS 8 RS 422 485 DB 9 Male 8 RS 232 DB 9 Male 8 SPECIFICATIONS 9 ENVIRONMENTAL SPECIFICATIONS 9 MANUFACTURING 9 POWER...

Page 3: ...COMMUNICATIONS COMMISSION STATEMENT 15 CANADIAN RADIO INTERFERENCE REGULATIONS 15 EMC DIRECTIVE STATEMENT 16 Figures Figure 1 Switch SW2 5 Figure 2 RS422 485 Interface Configuration 6 Figure 3 Electr...

Page 4: ...s that it does not require opening the computer case nor does it require resources such as I O ports or IRQ s It does require a system that supports USB both in terms of hardware and operating system...

Page 5: ...ther at the PC host or an upstream hub The OMG USB SER 2 is hot pluggable meaning there is no need to power down your computer prior to installation Connect the OMG USB SER 2 to an upstream host or hu...

Page 6: ...You can access your new COM ports by using the assigned COM identifiers as shown above In this case it is COM 3 and 4 However this assignment will vary from system to system At this point the hardwar...

Page 7: ...e box must be opened Do this by removing the four screws located on the bottom When reassembling please note that the top and bottom are keyed to fit in only one direction Electrical Interface Selecti...

Page 8: ...OFF No effect ON Connects TX to RX for two wire operation PU 485 option OFF for 422 OFF No effect ON Adds a 1 K ohm pull up resistor to RX PD 485 option OFF for 422 OFF No effect ON Adds a 1 K ohm pul...

Page 9: ...pedance when the device is not actively transmitting data NE 485 option OFF for 422 OFF The receiver is always enabled In a two wire setup the receiver will echo back all transmitted data ON The recei...

Page 10: ...unt is in the 232 position The switches will have no effect Port 2 RS 485 two wire communication with no echo The corresponding shunt is in the 422 485 position Switches 485 2 NE 2 and Port 2 L L T PU...

Page 11: ...s for USB Enabled and port activity Connector Pin Assignments RS 422 485 DB 9 Male Signal Name Pin Mode GND Ground 5 TX Transmit Data Positive 4 Output TX Transmit Data Negative 3 Output RTS Request T...

Page 12: ...to UL 94V0 rating and are 100 electrically tested These printed circuit boards are solder mask over bare copper or solder mask over tin nickel Power Consumption This device is a high power USB device...

Page 13: ...E will be lit This should allow you to use the WinSSD utility and the supplied loopback plug to check communications The supplied loopback plug connects TD to RD If you decide to test the Modem Contr...

Page 14: ...n a computer ready to run diagnostics 3 Omega Engineering maintains a home page on the Internet Our home page address is www omega com The latest software updates and newest manuals are available via...

Page 15: ...c states The RS 232 and the EIA TIA 574 specification define two types of interface circuits Data Terminal Equipment DTE and Data Circuit Terminating Equipment DCE The OMG USB SER 2 is a DTE device RS...

Page 16: ...and 32 receivers to be connected to one line This interface is ideal for multi drop or network environments RS 485 tri state driver not dual state will allow the e lectrical presence of the driver to...

Page 17: ...f a pre defined number of stop bits usually 1 1 5 or 2 An extra bit used for error detection is often appended before the stop bits Remain Idle or next start bit Odd Even or Unused STOP P BIT 5 to 8 D...

Page 18: ...e separation between the equipment and receiver Connect the equipment into an outlet on a circuit different from that to which the receiver is connected Consult the dealer or an experienced radio TV t...

Page 19: ...022 Class B Limits and methods of measurement of radio interference characteristics of information technology equipment EN55024 Information technology equipment Immunity characteristics Limits and met...

Page 20: ...shall not exceed the purchase price of the component upon which liability is based In no event shall OMEGA be liable for consequential incidental or special damages CONDITIONS Equipment sold by OMEGA...

Page 21: ...city Indicators Turbine Paddlewheel Systems Totalizers Batch Controllers pH CONDUCTIVITY pH Electrodes Testers Accessories Benchtop Laboratory Meters Controllers Calibrators Simulators Pumps Industria...

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