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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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JTAGDebugInterface

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ThePicoE‐14isequippedwithaJTAGdiagnosticportthatallowsreal‐timedebuggingofhardware,

firmwareandsoftware.UseoftheexternalJTAGportdisablesfourexternalGPIOpinsaswellasthe

internalJTAGloopback.

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SomeJTAGprogramsrequirethelengthoftheinstructionregister(IR).TheIRlengthislistedbelowfor

alldevicesintheJTAGchain.

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Device Instructionregisterbitlength

 FX20 FX60

FPGA 10 14

TurboLoader 8

EthernetPHY 8

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FPGA

PowerPC

IR= 10

EthernetTurbo Loader

TDI TDO

IR= 8

IR= 8

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Figure4

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ThePrimaryImageintheFlashROMcontainsanembeddedJTAGdiagnosticport.Thisallowsauserin

WindowsorLinuxtodebugsoftwarewithoutanexternalJTAGcable.TheinternalJTAGdiagnosticloop

backlooksjustlikeaParallelPortIVdiagnosticcablewhenusedwiththePicoE‐14driver.

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FX20: IR = 10

FX60: IR = 14

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