Virtex-4 FPGA Configuration User Guide www.xilinx.com 109UG071 (v1.12) June 2, 2017Readback Command SequencesRConfiguration Memory Read Procedure (1532 JTAG)The IEEE 1532 JTAG readback procedure differs slightly from the IEEE 1149.1 JTAGreadback procedure in that readback commands are not sent to the configuration logicthrough the CFG_IN JTAG register, rather the ISC_READ JTAG register is used to readconfiguration memory directly.At the end of 1532 JTAG readback, CRC Error status must be cleared by issuing Reset CRCcommand or writing the correct CRC value to CRC register. The 1532 JTAG readbackprocedure is illustrated in Figure 8-3.Figure 8-3: IEEE 1532 JTAG Readback FlowTable 8-6: Readback FilesFileExtensionFileTypeBitGenSetting Description.rba ASCII -b and -gReadbackAn ASCII file that contains readback commands, rather thanconfiguration commands, and expected readback datawhere the configuration data normally is. This file must beused with the .msk file.rbb Binary -gReadbackBinary version of .rba file. This file must be used withthe .msk file..rbd ASCII -gReadbackAn ASCII file that contains only expected readback data,including the initial pad frame. No commands are included.This file must be used with the .msd file.STARTLoad ISC_ENABLELoad ISC_DISABLEGo to Test Logic ResetLoad ISC_READLoad ISC_PROGRAMLoad ISC_PROGRAMRTI minimum12 TCK cyclesRTI minimum12 TCK cyclesRTI1 TCK cycleRTI1 TCK cycleLoad 32 bits ofbitstream dataLoad Reset CRCcommandLoad 5'b00000NYNYASTOPAShift 37 bits ofreadback data +statusEODataEObitstreamUG071_50_081404
