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???
10/20/06 16:06
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 		 #126808 - Big Flash - coda and data!
Responding to: ???'s previous message
The idea of having the flash mappable to XDATA space is an excellent one!

Normally, constants, strings, etc just waste CODE space; so significant CODE space can be freed-up by moving them into XDATA - provided you can have some flash in XDATA space.

Keil support this with their XCONST option.

I worked on a project that did this with a Triscend TE5 (now Zylogic ZE5) - you might want to take a look at the way they did it.

Triscend had a 32-bit external address bus, and SFRs that could map any of it into anywhere in CODE and/or XDATA space(s).

Another use for lots of flash (even if you're not doing code banking) is for in-application firmware updates - you load the spplication into a "spare" flash "page", and only switch to executig from that page once you're certain that the new image is complete & correct.
We had this planned on the Triscend, and I did some tests with it, but it was never fully deployed.

Triscend had a couple of application notes on it.

List of 59 messages in thread
TopicAuthorDate
How much flash should an 8051 have?            01/01/70 00:00      
   enough            01/01/70 00:00      
      Code Flash VS Data Flash            01/01/70 00:00      
         hints            01/01/70 00:00      
            Max Clock Speed, Etc.            01/01/70 00:00      
               that\'s a cop-out            01/01/70 00:00      
                  Not a cop-out            01/01/70 00:00      
                     can you sell it for less than $1.41            01/01/70 00:00      
                        Replacement costs            01/01/70 00:00      
                           then please stop arguing one point from the perspe            01/01/70 00:00      
                              The replacement market            01/01/70 00:00      
                                 How will that help?            01/01/70 00:00      
                                    Flash Reliability            01/01/70 00:00      
                                       not really - look out            01/01/70 00:00      
                                          More on Flash Reliability            01/01/70 00:00      
                                             XRAM replacement            01/01/70 00:00      
                                                Write-While-Fetch            01/01/70 00:00      
                                    That does not appear to be the target.            01/01/70 00:00      
                                       6/12 Clock Mode and XDATA support            01/01/70 00:00      
                     Have you looked at the one-clockers?            01/01/70 00:00      
                        How do you propose to fit that in the instruction            01/01/70 00:00      
                           map registers            01/01/70 00:00      
               clock speed            01/01/70 00:00      
                  Not a bad idea ... that's what Dallas did!            01/01/70 00:00      
                     Clock Speed Reduction            01/01/70 00:00      
                        if you knew the chip            01/01/70 00:00      
                           actually, it does either speed up or slow-down            01/01/70 00:00      
                              Variable clock speed            01/01/70 00:00      
                                 clock vs power            01/01/70 00:00      
                                    SIngle clock power            01/01/70 00:00      
               when i did this            01/01/70 00:00      
                  0.35u process & 64K            01/01/70 00:00      
         Big Flash - coda and data!            01/01/70 00:00      
            Does Zylogic = Triscend?            01/01/70 00:00      
               Zylogic; Triscend            01/01/70 00:00      
            that should make it clear            01/01/70 00:00      
         Data Apps            01/01/70 00:00      
   bank switching mechanism (RFC)            01/01/70 00:00      
      Bank Switching            01/01/70 00:00      
         that's how it's done traditionally ...            01/01/70 00:00      
         Keil support            01/01/70 00:00      
      bank switching no0t needed            01/01/70 00:00      
         "bank switching no0t needed"            01/01/70 00:00      
            if you read it all            01/01/70 00:00      
               I'd even tend to believe...            01/01/70 00:00      
      No lock IRQ            01/01/70 00:00      
   Parkinson's Law...            01/01/70 00:00      
   The trouble with PLLs            01/01/70 00:00      
      nearly every ARM has a PLL            01/01/70 00:00      
   yeah i understand that            01/01/70 00:00      
      ethernet mac            01/01/70 00:00      
   Dougal was..            01/01/70 00:00      
      Sorry to hear about your misfortune            01/01/70 00:00      
   no not seriously            01/01/70 00:00      
      I don't think he hates you, Jez            01/01/70 00:00      
      That must be the most painful            01/01/70 00:00      
         it's not a killer, but you do notice it            01/01/70 00:00      
   well jasmine can ride him all day            01/01/70 00:00      
   Gives a new meaning to that old interview question            01/01/70 00:00      

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