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4.1.1 pdata access by SFR

With the upcome of devices with internal xdata and flash memory devices using port P2 as dedicated I/O port is becoming more popular. Switching the high byte for pdata access which was formerly done by port P2 is then achieved by a Special Function Register. In well-established MCS51 tradition the address of this sfr is where the chip designers decided to put it. Needless to say that they didn't agree on a common name either. As pdata addressing is used in the startup code for the initialization of xdata variables a separate startup code should be used as described in section 3.11.



Bernhard Held 2004-02-21