topic About AC spec for SDHC in Vybrid Processors

About AC spec for SDHC

keisukewatanabe — Thu, 01 Aug 2013 10:27:26 GMT

Dear support,

I have a question about AC spec of SDHC in datasheet p,76.

Does the value of SD2 and SD3 not have the frequency dependence?

When I use it in 25Mhz, I suppose the minimum to be 7ns, I think whether matching does not match the SD side.

Please teach it when other value include frequency dependence.

When SD6 is maximum 8.3ns and SD2 is minimum 7ns, I think that can not output the signal by the next rise.

Is the rise of SD6 reliable by a fall?

Best regards,

Keisuke Watanabe

Re: About AC spec for SDHC

naoumgitnik — Fri, 02 Aug 2013 22:59:42 GMT

Dear Keisuke,

I guess we are talking about an interface used with an SDHC card.

May you be more design-specific, please?

Is your Vybrid-based design experiencing any issues while communicating with a card? If so, then what card type, in which circumstances, etc., please?

Sincerely, Naoum Gitnik.

Re: About AC spec for SDHC

keisukewatanabe — Tue, 06 Aug 2013 04:33:38 GMT

Dear Naoum,

I think that there is a conflict in the Table 61. SDHC switching specifications of datasheet.

In the following cases, I think the data will be not valid.

SD1=50Mhz

SD2=7ns

SD6=8.3ns(max)

In this case, what is the workaround?

Please tell me, if this idea is wrong.

Best regards,

Keisuke Watanabe

Re: About AC spec for SDHC

keisukewatanabe — Tue, 06 Aug 2013 11:01:24 GMT

Dear Naoum,

About Table 61. SDHC switching specifications, I am considered as follows.

When SD1 is 50MHz, SD2 and SD3 is 7ns.

When SD1 is 25Mhz, SD2 and SD3 is 17ns.

SD2=SD3 : According to datasheet.

SD4=SD5: According to datasheet.

i.e. SD1=SD2+SD3+SD4+SD5

Is this idea right?

Best regards,

Keisuke

Re: About AC spec for SDHC

naoumgitnik — Tue, 06 Aug 2013 22:56:39 GMT

Dear Keisuke,

Unfortunately, it is quite difficult to know all the details from the Reference Manual counting a few thousand pages, e.g. timing requirements for standard interfaces usually copied from their specifications.

Based on my experience, much more efficient is focusing on actual problems observed in the customers' designs.

Sincerely, Naoum Gitnik.

Re: About AC spec for SDHC

keisukewatanabe — Wed, 07 Aug 2013 01:36:33 GMT

Dear Naoum,

I will ask the same question again.

================

About Table 61. SDHC switching specifications, I am considered as follows.

When SD1 is 50MHz, SD2 and SD3 is 7ns.

When SD1 is 25Mhz, SD2 and SD3 is 17ns.

SD2=SD3 : According to datasheet.

SD4=SD5: According to datasheet.

i.e. SD1=SD2+SD3+SD4+SD5

Is this idea right?

================

Does it mean that it is difficult to reply this question?

Best regards,

Keisuke Watanabe

Re: About AC spec for SDHC

karina_valencia — Fri, 30 Aug 2013 20:59:16 GMT

naoumgitnik can you continue with the follow up on this case?