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Re: Early 8051 variants with dual dptr (AMD?)

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Am 30.06.2016 um 06:15 schrieb rickman:

> With multiple DPTR registers, wouldn't the instruction set be
> modified making it no longer code compatible?

Of course not.  That would be silly.

> Or is the DPTR register
> switched out by some mechanism that is essentially transparent to
> existing code?

The 8051 has an entire dedicated memory space for "special function 
registers".  The obvious place to put the switch that flips the two 
available DPTRs is in there.

Normal compiled code won't get to use the additional DPTR, though.  It 
would be used mainly to speed up optimized or inlined versions of stuff 
like memcpy(), memset() etc.  It was great fun to deal with this in 
assembly, though.

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Early 8051 variants with dual dptr (AMD?) Philipp Klaus Krause <pkk@spth.de> - 2016-06-29 09:49 +0200
  Re: Early 8051 variants with dual dptr (AMD?) Philipp Klaus Krause <pkk@spth.de> - 2016-06-29 11:19 +0200
    Re: Early 8051 variants with dual dptr (AMD?) Martin Riddle <martin_ridd@verizon.net> - 2016-06-29 22:52 -0400
      Re: Early 8051 variants with dual dptr (AMD?) Martin Riddle <martin_ridd@verizon.net> - 2016-06-29 23:28 -0400
        Re: Early 8051 variants with dual dptr (AMD?) rickman <gnuarm@gmail.com> - 2016-06-30 00:15 -0400
          Re: Early 8051 variants with dual dptr (AMD?) Philipp Klaus Krause <pkk@spth.de> - 2016-06-30 09:37 +0200
          Re: Early 8051 variants with dual dptr (AMD?) Martin Riddle <martin_ridd@verizon.net> - 2016-06-30 08:26 -0400
          Re: Early 8051 variants with dual dptr (AMD?) Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2016-06-30 22:52 +0200
            Re: Early 8051 variants with dual dptr (AMD?) Philipp Klaus Krause <pkk@spth.de> - 2016-07-01 08:06 +0200
        Re: Early 8051 variants with dual dptr (AMD?) Philipp Klaus Krause <pkk@spth.de> - 2016-07-07 01:19 +0200
      Re: Early 8051 variants with dual dptr (AMD?) Philipp Klaus Krause <pkk@spth.de> - 2016-06-30 09:28 +0200

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