Black Box RS422/485, RS-232/422/485 manual Appendix B. Electrical Interfaces, RS-422

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DUAL- AND QUAD-PORT USB HUBS

Appendix B. Electrical Interfaces

B.1 RS-232

Quite possibly the most widely used communication standard is RS-232. This implementation has been defined and revised several times and is often referred to as EIA/TIA-232.

The IBM® PC AT® computer defined the RS-232 port on a DB9 connector, and subsequently the EIA/TIA approved this implementation as the EIA/TIA-574 standard. This standard is defined as the 9-PositionNon-Synchronous Interface between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange. Both implementations are in widespread use and are referred to as RS-232 in this document.

RS-232 is capable of operating at data rates up to 20 kbps at distances less than 50 ft. (15.2 m). The absolute maximum data rate may vary due to line conditions and cable lengths. RS-232 is a single-ended or unbalanced interface, meaning that a single electrical signal is compared to a common signal (ground) to determine binary logic 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 USB Hub is a DTE device.

B.2 RS-422

The RS-422 specification defines the electrical characteristics of balanced-voltage digital interface circuits. RS-422 is a differential interface that defines voltage levels and driver/receiver electrical specifications.

On a differential interface, logic levels are defined by the difference in voltage between a pair of outputs or inputs. In contrast, a single-ended interface, for example RS-232, defines the logic levels as the difference in voltage between a single signal and a common ground connection.

Differential interfaces are typically more immune to noise or voltage spikes that may occur on the communication lines. Differential interfaces also have greater drive capabilities that allow for longer cable lengths. RS-422 is rated up to 10 Mbps and can have cabling 4000 feet (1219.2 m) long. RS-422 also defines driver and receiver electrical characteristics that will allow 1 driver and up to 32 receivers on the line at once. RS-422 signal levels range from 0 to +5 volts. RS-422 does not define a physical connector.

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Contents July IC1020A IC1021A IC1022A Federal Communications Commission EMC Directive Statement DUAL- and QUAD-PORT USB HubsNOM Statement DUAL- and QUAD-PORT USB Hubs Trademarks Contents Specifications Overview IntroductionWhat’s Included Technical DescriptionSignal Name Pin # Mode Connector Pin AssignmentsSignal Name Operating System Installation InstallationSystem Installation Installation Original Configuration ConfigurationElectrical Interface Selection Jumpers E5, E6, E7, and E8Jumper Port RS-232 RS-422/485 Switch SW4 SettingsSwitch SW3 Settings SwitchDescription RS-485 RS-422 Switch SW2 and SW4 Settings Switch Port Description RS-485Switch SW1 and SW3 Settings QUAD-PORTUSB HUB-RS-232/422/485 IC1022A Port Description RS-485Jumpers E1, E2, E3, E4, E5, E6, E7, and E8 Switch Port Description RS-485 RS-422 SettingSetting Troubleshooting Tips Appendix A. TroubleshootingShipping and Packaging Calling Black BoxRS-232 Appendix B. Electrical InterfacesRS-422 RS-485 Appendix C Asynchronous Communication Figure C-1. Bit diagram for asynchronous communicationAppendix C Asynchronous Communication Copyright 2002. Black Box Corporation. All rights reserved