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Pico Communications E-14 Computer Hardware User Manual

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E‐14HardwareReferenceManual www.picocomputing.com PicoComputing,Inc.

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*PleaserefertotheAnalogInterfaceSelectionGuideinAppendixEforcompatible8‐12‐bitconverters

RS‐232SerialTransceiver

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ThePicoE‐14containsoneasynchronousRS‐232serialtransceiverthatalsomeetsEIA/TIA‐232and

V.28/V.24specificationsatamaximumdatarateof250kBps.Becausetheserialtransceiverisdirectly

connectedtotheFPGAanybithigh‐levelprotocolcanbeimplementedinlogic.PicoComputing

supportsvariousasynchronous,synchronousandmilitaryserialprotocols.

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RS‐232isthemostcommonphysicallayerprotocolforserialdata.Itisthestandardusedonserialmice

forcomputers,modems,consumerGPSreceiversandevensomemilitaryradios.Onlyonewireis

neededtosendasignalonanRS‐232link.AtotaloftwodevicesareallowedonasingleRS‐232link.

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Inaddition,therearetwopossiblelogicstatesonanRS‐232line(highandlow).Thehighvoltageis

positiveandthelowvoltageisnegative.

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PhysicalLayerSpecifications:

Standard Noise

Immunity

Max

Distance

Max

Speed

Max

Connections

RS‐232

Satisfactory 50ft 250kBps* 1Tx/1Rx

*Maximumspeeddecreaseswithincreasedcablelength.

*TheoldRS‐232,422and485standardsarenowobsoleteandhavebeenreplacedbyEIA/TIA‐232,422

and485.

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SerialTransceiverSpecifications:

MaximumContinuousPositiveInputVoltage +25VDC

MaximumContinuousNegativeInputVoltage‐25VDC

ESDProtectionLimit +/‐15,000V

MaximumShortCircuitDurationonOutput Infinite

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TypicalRS‐232OutputVoltage +/‐5.4V

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RS‐232MaximumLowInputThreshold* 1.2V

RS‐232MinimumHighInputThreshold 1.5V

*RS‐232Receiverscanacceptdigitalinputs

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