[SI-LIST] Re: Displaying eye pattern in an oscilloscope?
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Ihsan Erdin <erdinih@xxxxxxxxx>, Chris.Cheng@xxxxxxxxxxxx
- Date: Sun, 23 Oct 2005 05:24:15 -0700
Ishan, I do agree with you that just triggering on DQS and running
infinite persistence will just make an ugly mess on the screen. And if
what one wants to do is detailed characterizations by: target/source DIMM,
interleaved/non-interleaved bursts etc, what I suggest is inadequate.
However, for the very same reason that infinite persistence without a cycle
type trigger doesn't work well, we can extract reads and writes using only
DQS and DQ. The trick is to use the 90 / 0 DQS to DQ phase offset of write
versus read as a post-process filter to separate out the reads from the
writes in .wfm captures. If the idea is to verify that system level
timing works, that should be enough for the data path. If the skew moves
around by more than 90 degrees such that reads can't be distinguished from
writes, then the channel is broken anyway.
Regards,
Steve.
At 11:14 PM 10/22/2005 -0400, Ihsan Erdin wrote:
>I'm not sure if it's possible at all. To capture a read or write cycle,
>you'll need a logic triggering setup for data and control signals (/WE,
>/CS) as Chris describes. For an eye diagram pattern, on the other hand,
>you'll need an edge trigger setup either at the clock or the data itself
>with a delay (one or two periods) A logic triggering with an infinite
>persistence display setting will not result an eye diagram.
>
>Ihsan Erdin
>
>On 10/22/05, Chris Cheng
><<mailto:Chris.Cheng@xxxxxxxxxxxx>Chris.Cheng@xxxxxxxxxxxx> wrote:
>>Not that simple.
>>You will most like need some advanced triggering to trigger on CAS, WE so
>>that you can tell if it is a read or write. Then you probably need some
>>software to limit the hit to certain address to be sure you get the right
>>DIMM. Good luck if you need to see the effect of interleave vs.
>>non-interleave.
>>________________________________
>>
>>From: <mailto:si-list-bounce@xxxxxxxxxxxxx>si-list-bounce@xxxxxxxxxxxxx
>>on behalf of steve weir
>>Sent: Fri 10/21/2005 10:59 PM
>>To: <mailto:rrepollo@xxxxxxxxxxxxxxxx>rrepollo@xxxxxxxxxxxxxxxx;
>><mailto:si-list@xxxxxxxxxxxxx>si-list@xxxxxxxxxxxxx
>>Subject: [SI-LIST] Re: Displaying eye pattern in an oscilloscope?
>>
>>
>>
>>Don't you have access to both clock and data?
>>
>>
>>Steve
>>At 09:17 AM 10/22/2005 +0800, Rep wrote:
>> >Good day!
>> >
>> >I simulated a data signal from SH4 processor to SDRAM, displaying it in an
>> >eye pattern.
>> >I need to verify the signal by actual board evaluation.
>> >Could please someone tell me how I could measure the
>> >signal in eye pattern through the use of an oscilloscope (TEK)?
>> >
>> >I would really appreciated any help I could get.
>> >
>> >Thank you.
>> >
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