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???
10/02/09 14:46
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 		 #169360 - That's what the capital B means ...
Responding to: ???'s previous message
Maarten Brock said:
Richard Erlacher said:
The [...] specification v1.9 [...] has a maximal clock rate of 25 MHz, and, therefore a data rate in 4-bit mode of 50 MBps, albeit in whatever bursts the SD card chooses to generate.


Just out of curiosity, how does that work? You do mean 50 MByte/s don't you?

Gee ... I thought it was obvious ... 25 Mbps * 4 ... in bursts, of course ... I guess I need to get out more ...

Richard Erlacher said:
Now, if one uses built-in MCU features to handle SPI communication, the speed is considerably slower. The SD card spec indicates SPI can be used at up to 25 MHz. I'm not convinced the hardware support in any 805x-class MCU can handle that high a rate.

All SiLabs chips including those up to 100 MHz can run SPI at 12.5 MHz. I know no faster SPI in an 8051.

Maarten


MBps = MegaBytes per second
Mbps = Megabits per second

RE


List of 55 messages in thread
TopicAuthorDate
I've asked this before ... but ...            01/01/70 00:00      
   Is this specifically 8051?            01/01/70 00:00      
      specifically with 805x and NO SD-specific hardware on-chip            01/01/70 00:00      
         There often are huge speed differences            01/01/70 00:00      
   Yep I have            01/01/70 00:00      
      I'd be interested in that ...            01/01/70 00:00      
         Ill send you a schematic            01/01/70 00:00      
            What do points mean?            01/01/70 00:00      
            Well, I haven't seen it ... yet            01/01/70 00:00      
               Oh dear; I hope this wasn't Jez, then...            01/01/70 00:00      
   How fast?            01/01/70 00:00      
      I'm using an old, but relatively complete, spec            01/01/70 00:00      
         "external" hardware            01/01/70 00:00      
            Yes, that would be nice ...            01/01/70 00:00      
         50MBps            01/01/70 00:00      
            That's what the capital B means ...            01/01/70 00:00      
               You assume too much            01/01/70 00:00      
                  It's like that other nomenclature issue I keep mentioning            01/01/70 00:00      
                     Sad, but true            01/01/70 00:00      
               25MHz * 4bit = 12.5MB/s            01/01/70 00:00      
                  correct            01/01/70 00:00      
                  Now I'm confused ... as you can see ...            01/01/70 00:00      
                     someplace to put spec's            01/01/70 00:00      
                        It's a two-edged sword            01/01/70 00:00      
                           True, but..            01/01/70 00:00      
                              Published spec's are in the public domain            01/01/70 00:00      
                                 No, that's not true            01/01/70 00:00      
                                    It depends on how the IP is used, doesn't it?            01/01/70 00:00      
                                       No, it doesn't.            01/01/70 00:00      
                                          Not public domain            01/01/70 00:00      
                                             Quite so!            01/01/70 00:00      
                                             Copyright Term and the Public Domain in the United States            01/01/70 00:00      
                                                They have the "right" but not the cause            01/01/70 00:00      
                                                   Letter of the law            01/01/70 00:00      
                                                      Let me ask you something ...            01/01/70 00:00      
                                                         I didn't say that            01/01/70 00:00      
                                                   They have the right            01/01/70 00:00      
                                                      When was the last time you saw a written copyright?            01/01/70 00:00      
                                                         See previous examples!            01/01/70 00:00      
                                                            Whose interests are "protected"?            01/01/70 00:00      
                                                               Information owners            01/01/70 00:00      
                                                                  ?            01/01/70 00:00      
                                                                     Life isn't fair            01/01/70 00:00      
                                                               What the thread is about? SD Card or CopyRights!!!            01/01/70 00:00      
                                                                  There's a reason for that ...            01/01/70 00:00      
                                                                     Lots of interests in SD, but danger involved in sharing            01/01/70 00:00      
                                                         last time I saw a written copyright ...            01/01/70 00:00      
                                                            No need for long legalese            01/01/70 00:00      
                                                               True, but ...            01/01/70 00:00      
                                                            That's the boilerplate to which I referred            01/01/70 00:00      
                                                               the band won            01/01/70 00:00      
                                                      Ooops!            01/01/70 00:00      
   I forgot sorry            01/01/70 00:00      
      That was what ... 6 weeks ago?            01/01/70 00:00      
   SD/SDIO host controller chips            01/01/70 00:00      

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