结构体问题

只看该作者 · 2015-6-5 08:35

用的芯片是MC56F84462,CW版本10.6
工程中定义了结构体，结构体中都是对位的定义，比如
typedef union
{
unsigned long LONG;
struct
{
unsigned short L_FLAG;//低位
unsigned short H_FLAG;//高位
} WORD;
struct
{
unsigned long RELAY             :1;
unsigned long SERCH_FR       :1;//
unsigned long VOL_END       :1;//
unsigned long SERCH_RST    :1;
                  unsigned long STOP_E0       :2;
unsigned long CLR_E0       :1;
unsigned long FIRST       :1;
unsigned long START       :2;
unsigned long RST_START :1;
unsigned long VOL_SH_ST    :1;
unsigned long VOL_SH_END    :1;
unsigned long SERCH_START    :1;
unsigned long DC_START    :2;

      unsigned long ABORT_REVERT :1;
      unsigned long WR_FLASH_START  :1;
unsigned long PRE_SHUT       :1;
unsigned long PASSWORD       :1;//密码锁定
unsigned long MD    :2;//
unsigned long RX_DATA_LEN    :1;
unsigned long TREF    :1;
unsigned long END       :1;
unsigned long OWNER_DATA    :1;
unsigned long COMM_END       :1;//
unsigned long LT_LED       :1;//
unsigned long LV_LED       :1;//
unsigned long VOL_TRIG       :1;//
unsigned long VOL_BREAK_FULL  :1;//
unsigned long DC_FLAG       :1;//
} BIT;

} flag_val;
程序中对位可以直接进行赋值，但是芯片是怎么执行赋值过程的呢，对于val.BIT.DC_FLAG=1是先进行清零再赋值1？