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                                 Listing 2


#define LAMP_REG_1 (*((char *) (0x2808)))
#define LAMP_REG_2 (*((char *) (0x2800)))

unsigned char shadow_1 = 0;
unsigned char shadow_2 = 0;

enum LAMPS { RUN_LAMP, ERROR_LAMP, SETUP_LAMP, ALIGN_LAMP,
             ALERT_LAMP, SURVEY_LAMP, BIT_LAMP, SPARE_1,
             BATT_LAMP, CHARGE_LAMP, ZONE_LAMP, EAST_LAMP,
             SPARE_2, SPARE_3, SPARE_4, SPARE_5, MID = 7 };

/*----------------------------------------------------------------------------
MACRO to turn on a specific lamp. Use of literals of type LAMPS 
for the parameter.
----------------------------------------------------------------------------*/
#define turn_on( lamp ) \
( \
     (lamp > MID) ? \
     ( \
          ( ( shadow_1 |= ( ( 1 << (lamp - 8) ) & 0xFF ) ) ) ,
           (LAMP_REG_ 1 = shadow_1 )
     ) \
     : \
     ( \
          ( ( shadow_2 |= ( (1 << lamp) & 0xFF ) ) ) , \
          LAMP_REG_1 = shadow_2) \
     ) \
) \

/*----------------------------------------------------------------------------
MACRO to turn off a specific lamp. Use literals of type
LAMPS for the parameter.
----------------------------------------------------------------------------*/
#define turn_off( lamp ) \
( \
     (lamp > MID) ? \
     ( \
          ( shadow_1 &= ( ~( 1 << (lamp-8) ) & 0xFF) ), \
          ( LAMP_REG_1 = shadow_1 ) \  
     ) \
     : \
     ( \
          ( shadow_2 &= ( ~(1 << lamp) ) & 0xFF ) ) , \
          ( LAMP_REG_2 = shadow_2 ) \
     ) \
) \

Note the use of the trinary operator instead of a control
structure to decide which shadow register and lamp latch to
update. The call to these macros looks like this:

     turn_on( RUN_LAMP ) ;
     turn_off( RUN_LAMP ) ;      


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