Apple II
File Type Notes
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                                                  Developer Technical Support

File Type:         $5A (90)
Auxiliary Type:    $0002

Full Name:     Battery RAM saved configuration
Short Name:    Battery RAM configuration

Written by:    Matt Deatherage                                       May 1990

Files of this type and auxiliary type contain images of Apple IIgs Battery 
RAM.
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Since the IIgs battery-powered RAM contains important system parameters and 
control information, many utility programs would like to save an image of all 
these parameters for later restoration.  This ability can be handy when 
changing batteries or in a classroom situation where students may change text 
colors and preferences to suit their individual tastes--without regard for the 
teacher who has to restore the machine to normal operation for the next class.

Apple has defined the following simple file format for use in such instances.


The File Format

The file format contains a safety catch to prevent parameters defined for new 
machines from interfering with older machines.

ROMVersion    (+000)    Word            The version number of the 
                                        Apple IIgs ROM for the machine on 
                                        which this file was created.  The 
                                        file should only be restored on 
                                        machines of the same ROM version.  
                                        For example, if this value is $0003, 
                                        the image of Battery RAM should not 
                                        be written to a ROM 01 machine.  
                                        Instead, warn the user of the 
                                        incompatibility.
BRAM          (+002)    256 Bytes       256 bytes of battery RAM 
                                        image.  This is obtained from the 
                                        ReadBRam tool call and should be 
                                        restored (where appropriate) with 
                                        the WriteBRam tool call.


Further Reference
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  o  Apple IIgs Firmware Reference
  o  Apple IIgs Toolbox Reference, Volume 1

