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Re[2]: JTAG/Boundary Scan



     
     On a related subject,does anybody know of an x86-based PCI motherboard 
     that does support JTAG ? I'd like to be able to test PCI-boards 
     in-situ.
     
     
     Richard Rooney,
     Mentec,
     Dublin,
     Ireland.
     
     
     ______________________________ Reply Separator 
     _________________________________ Subject: Re: JTAG/Boundary Scan
     Author:  pci-sig-request@znyx.com at internet-mail Date:    02/08/96 
     14:21
     
     
     Reza Vahedi wrote:
     > 
     > Hi,
     > I am a little confused by the PCI2.1 specification regarding > the 
     JTAG/Boundary Scan signals.
     > I do not intend to support PCI JTAG. I am trying to figure out > 
     what I should do with the JTAG pins.
     > Section 2.2.10 of the spec. says the following: > 
     > Expansion boards that do not support the IEEE 1149.1 interface 
     should > hardwire the board's TDI pin to its TDO pin.
     > 
     > Section 4.3.3 says the following:
     > ..if boundary scan is not implemented on the planar, TMS and TDI > 
     should be independently bused and pulled up each with ~5Kohm
     > resistors, and TRST# and TCK should be independently bused
     > and pulled down, each with ~5K ohm resistors. TDO should be left 
     open. > 
     > Do I need to implement pull-up/pull-downs as stated in 4.3.3 or can 
     > I just hardwire TDI and TDO as stated in 2.2.10?
     > 
     > Reza Vahedi
     > rvahedi@cognex.com
     
     It depends on what you're designing. Section 2.2.10 refers to 
     expansion boards and section 4.3.3 refers to the motherboard (it 
     begins by :
     "PCI control signals always requires pull-up resistors on the 
     motherboard (NOT the expansion board) to ensure ...")
     
     If you design an expansion card and not support JTAG on you board you 
     should hardwire TDI to TDO to ensure the continuity of the JTAG chain.
     
     if you design a motherboard you should follow section 4.3.3.
     
     
     Didier Lachieze
     Hewlett-Packard
     
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