B&B Electronics 485DSS manual Operation

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Operation

The host computer of the RS-485 network controls each 485DSS on the network by sending them command messages. These commands can turn a 485DSS on or off, and can also request status from an individual or from all of the 485DSS's on the network. The communication setup used to send and receive these commands are: 9600 baud, 8 data bits, no parity, and 1 stop bit. Each command consists of four characters: a start of message character, two address characters, and the command character. All 485DSS's on the network will receive the command message strings sent by the Host, but only the 485DSS with the matching address will execute the command. Execution of the ON command raises the Request To Send (RTS) output line on pin 4 of the DB25 connector and connects the RS-232 port to the RS-485 network. Once ON (selected), the RS-232 device can transmit and receive data to the HOST. Executing the OFF command lowers the RTS line, disconnecting the RS-232 port from the network. The RS-232 port of the 485DSS is OFF (not selected) at power up. The 485DSS does not buffer or delay any data passing through the unit. ALL data that is sent from the RS-485 device will be passed through to the RS-232 side while the unit is selected including the next set of command characters.

The Host can poll any or all 485DSS's on the network using the request status command. This allows the Host to determine if any 485DSS is requesting access to the network by monitoring the handshake status character returned by the 485DSS. The status character reflects the state of the input handshake signal Clear To Send (CTS) on the RS-232 connector pin 5. With this feature the Host has the ability to prioritize each 485DSS on the network. Refer to Figure 2.

8485DSS-0308 Manual

B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104 B&B Electronics – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353 91 792444 – Fax +353 91 792445

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Contents Electronics Mfg. Co. Inc Designed and Manufactured Ottawa, IllinoisInternet 485DSS-0308 Manual CoverPage Table of Contents IiTable of Contents 485DSS-0308 Manual Checklist Hardware IntroductionSpecifications Port ConfigurationRS-485/422 Port RS-422/485 Port Terminal Block Signal Description Direction Signal Ground +12VDC Power Supply InputRS-232 Port Clear to Send Input Signal Ground RS-422/485 WiringWire Mode Frame Ground Transmit Data Output Receive Data InputComponent Values For Send Data Timing RS-485 Wiring Diagram Wire Mode Power Supply RS-422 Wiring Diagram RS-485 and RS-422 TerminationOperation Communication Configuration Distributed Smart Switch CommandsCommand String On CommandDecimal HexOFF Command Status Request CommandPage ACK Setting the 485DSS Address Address SwitchDIP Switch Binary File Transfer Software Description Appendix a Ascii Character Codes 485DSS-0308 Manual Appendix aPage Symbol Appendix B Decimal/Hexadecimal/ConversionsDec/Hex Conversions Decimal Hexadecimal 485DSS-0308 Manual Appendix BHexadecimal to Decimal Conversion Decimal to Hexadecimal ConversionAppendix C Cable Charts Chart 1. IBM PC DB25 Connector to 485DSS RS-232 DTE PortRS-232 DTE Port DB25 Connector Direction RS-232 DTE PortChart 6. RS-485 2-Wire Device to 485DSS RS-485/422 Port RS-485/422Device Direction Terminal Blocks
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