Edi, I assume you're worried about signal integrity (not = logic/functionality). Some troubleshooting tips to try: 1. measure noise on the Vref lines for both the FPGA and memory. I don't = remember offhand but I belieive max is around 30mV. Micron Tech has a = good DDR layout guide. 2. carefully measure 1.8V or 2.5V Vcc and Vtt noise (use an AC-coupled = 50 ohm coax soldered directly to a local bypass cap site. 3. Tie a probe to the DDR clock at the memory to trigger a high-speed = scope (> 4GHz). It's nice to have software write a test loop to generate = various read and write bit patterns on the memory bus (especially = alternating 00s and FFs). Probe each memory line and note under/over = shoot, jitter, Tsu and Th. Remember you have to probe D/DQ at the memory = for write data and at the FPGA for read data. 4. For Xilinx FPGAs, pay particular attention to undershoot (see their = appnote where they suggest running the memory bus drivers at .3V below = Vcc to prevent reverse biasing the clamps). I bet you'll find either excessive power supply noise, Vref noise, Vtt = noise, or under/over shoot Good Luck, Mike -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Fraiman, Edi Sent: Wednesday, August 02, 2006 4:01 PM To: Vinu Arumugham; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: DDRAM BUS Testing Yes, FPGA support JTAG. But JTAG frequency is low. JTAG test wasn't working because we are out of spec (minimum DDR operating frequency). =3D20 Best regards, =3D20 Edi Fraiman > -----Original Message----- > From: Vinu Arumugham [mailto:vinu@xxxxxxxxx]=3D20 > Sent: Wednesday, August 02, 2006 3:54 PM > To: Fraiman, Edi > Subject: Re: [SI-LIST] DDRAM BUS Testing >=3D20 >=3D20 > The FPGA does not support JTAG? >=3D20 > Thanks, > Vinu >=3D20 > Fraiman, Edi wrote: >=3D20 > >Hi, > >=3D20 > > > >I'm working on a design that includes FPGA with DDRAM controller = and=3D20 > >several DDRAM chips. The traces goings direct from FPGA to=3D20 > DDRAM with=3D20 > >necessary pulll up resistor to Vref. (SSTL interface)=3D20 > without any debug=3D20 > >connector. > > > >=3D20 > > > >Sometimes we have productions problems. It is very difficult to = find=3D20 > >what bit in bus between FPGA and DDRAM is shorted or disconnected. > > > >Could somebody give any tips how it's possible debug DDRAM busses = in=3D20 > >terms of production issues. > > > >=3D20 > >=3D20 > >Best regards, > >=3D20 > >Edi Fraiman > >=3D20 > > > > > > - - - - - Appended by Scientific Atlanta, a Cisco=3D20 > company - - - -=3D20 > >- > >This e-mail and any attachments may contain information=3D20 > which is confidential, proprietary, privileged or otherwise=3D20 > protected by law. The information is solely intended for the=3D20 > named addressee (or a person responsible for delivering it to=3D20 > the addressee). If you are not the intended recipient of this=3D20 > message, you are not authorized to read, print, retain, copy=3D20 > or disseminate this message or any part of it. If you have=3D20 > received this e-mail in error, please notify the sender=3D20 > immediately by return e-mail and delete it from your computer. > > > > > >------------------------------------------------------------------ > >To unsubscribe from si-list: > >si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > > >or to administer your membership from a web page, go to:=3D20 > >//www.freelists.org/webpage/si-list > > > >For help: > >si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > > >List FAQ wiki page is located at: > > http://si-list.org/wiki/wiki.pl?Si-List_FAQ > > > >List technical documents are available at: > > http://www.si-list.org > > > >List archives are viewable at: =3D20 > > //www.freelists.org/archives/si-list > >or at our remote archives: > > http://groups.yahoo.com/group/si-list/messages > >Old (prior to June 6, 2001) list archives are viewable at: > > http://www.qsl.net/wb6tpu > > =3D20 > > > > =3D20 > > >=3D20 - - - - - Appended by Scientific Atlanta, a Cisco company - - - - - = =3D This e-mail and any attachments may contain information which is = confident=3D ial, proprietary, privileged or otherwise protected by law. 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