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MSO9254A Logic Analyzer output shows I/O during "Update-DR" JTAG state

Question asked by jcwilli585 on Aug 11, 2015
Latest reply on Aug 14, 2015 by algoss
Hi all,

I'm using the digital Logic Analyzer probes on the MS09254A to debug an ARMv7 CPU with JTAG.  I did the setup and put the probes on the ground pin, TDI, TDO, TMS, and TCK.  The first part of the output looks fine.  Then the output shows that there's an accumulation of input and output (I/O) during JTAG states that it shouldn't.  Here's what I'm getting:

Time             TAP State          Opcode/Reg Len  Data                         
45e-9            Select-DR                                                      
141e-9           Capture-DR                                                     
245e-9           Shift-DR TDI                 4    11110000                     
245e-9           Shift-DR TDO                 4    10000000                     
645e-9           Exit1-DR                                                       
741e-9           Update-DR TDI                4    11110000                     
741e-9           Update-DR TDO                4    00010000                     
845e-9           Select-DR                                                      
19.645e-6        Select-IR                                                      
19.741e-6        Capture-IR                                                     
19.845e-6        Shift-IR TDI                 4    01010000                      
19.845e-6        Shift-IR TDO                 4    10000000                     
20.341e-6        Exit1-IR                                                       
22.645e-6        Update-IR TDI                4    10100000                     
22.645e-6        Update-IR TDO                4    00010000                        
22.741e-6        Select-DR                                                      
25.541e-6        Capture-DR                                                     
25.645e-6        Shift-DR TDI                 35   01000000 10000000 00000000 00000001 01000000
25.645e-6        Shift-DR TDO                 35   01000000 00000000 00000000 00000001 11100000
31.645e-6        Exit1-DR                                                       
31.741e-6        Update-DR TDI                35   01010000 00000000 00000000 00100000 01000000
31.741e-6        Update-DR TDO                35   11110000 00000000 00000000 00000000 01000000
31.845e-6        Idle                                                           
31.941e-6        Select-DR                                                      
34.845e-6        Capture-DR                                                     
34.941e-6        Shift-DR TDI                 35   11000000 00000000 00000000 00000000 00000000
34.941e-6        Shift-DR TDO                 35   01000000 00000000 00000000 00000001 11100000
40.741e-6        Exit1-DR                                                       
40.845e-6        Update-DR TDI                35   00000000 00000000 00000000 00000000 01100000
40.845e-6        Update-DR TDO                35   11110000 00000000 00000000 00000000 01000000

Any ideas on why I'm getting this?  

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