abstract.txt

Keil uVision2

*** IMPORTANT NOTE ***
    Far Memory Support is only available in the PK51 package.
    If you have an CA51, DK51, or Evaluation Package the far memory
    support is not available and this example will not work.

The T89C51RD2 EEPROM DEMO program shows you how to use the new
features of C51 Version 7 and LX51 Linker/Locater to access the 
data in the EEPROM area.

This files can be used as template for own projects.

XBANKING.A51 configures the expanded 'far' memory space as EEPROM space.

EEPROM.H  contains the data definitions that are stored in the EEPROM space.
EEPROM.C  defines the user class HDATA_EEPROM.  This user class is located
with the LX51 CLASSES directive into the address space X:0x020000 - X:0x0207FF.
This address space reflects the EEPROM memory of the 89C51RD2 device.  
In uVision2 the address range for the memory class is enter under Options for
Target - LX51 Locate - User's Classes.

For save interrupt behaviour of the application it is required to invoke
the C51 Compiler with the directive VARBANKING (1).  Therefore the uVision2
project enables under Project - Options for Target: 'far' memory type support 
and Save address extension SFR in interrupts.  During an interrupt, the register
EECON that is defined as ?C?XPAGE1SFR will be saved and set to 0.

This EEPROM space is simulated under uVision2 with the V: memory type prefix.
This memory space can be manipulated using standard uVision2 debugging commands.
For example:
   D V:0                            // displays the EEPROM memory space
   SAVE EEPROM.HEX V:0, V:0x7FF     // saves the EEPROM memory space
   LOAD EEPROM.HEX                  // loads the EEPROM contents

It is also possible to display variables in the EEPROM space using standard
uVision2 features, i.e. the Watch Window.  The mapping for the uVision2 debugger
is configured via the ?B?xMEM symbols in the XBANKING.A51 config file.