2017-2018-1 20155315 embedded C language test of the basic design of information security system

Hours requirements

Pseudo code

• Extract hours

1. Extract Time Address
   Time is stored in the 16-bit register (base +2), defining a time macro to store the address.

   #define Time_Addr 0xFFFFC0000#define TIME *(volatile int *) (Time_Addr+2)

2. According to the structure chart, the hours occupies 5 bits, and its address and time address are offset by 11, so when extracting the value, the original value is shifted to the right 11 bits.

   time>>11

3. When you move right, the value is 0x1f (00011111), and the lower five bits of the value are extracted, which is hours

   (time>>11)&0x1F

• Set hours

1. Place the original hours 0

   newtime = oldtime & ~(0x1F<<11);

2. Move the hours to the left by 11 bits, the other bit to 0, so that the hours is set to a new time after the left hours or the time of the previous step

   newtime  =newtime | ((hours&0x1F)<<11);

   Code implementation

   ```

   Define TIME_ADDR 0xffffc0000define time (volatile int ) (time_addr+2)

   int gethours ()
   {
   int time = time;
   Return (TIME>>11) &0x1F;
   }

void sethours (int hours)
{
int oldtime = time;
int newtime = oldtime & ~ (0X1F<<11);
NewTime =newtime | ((hours&0x1f) <<11);
Time=newtime;
}

## minutes

Define TIME_ADDR 0xffffc0000define Time (volatile int) (time_addr+2)

int getminutes ()
{
int time = time;
Return (TIME>>5) &0x3F;
}

void setminutes (int minutes)
{
int oldtime = time;
int newtime = oldtime & ~ (0x3f<<5);
NewTime =newtime | ((minutes&0x3f) <<5);
Time=newtime;
}

## seconds

Define TIME_ADDR 0xffffc0000define Time (volatile int) (time_addr+2)

int getseconds ()
{
int time = time;
Return time&0x1f;
}

void setseconds (int hours)
{
int oldtime = time;
int newtime = oldtime & ~0x1f;
NewTime =newtime | (seconds&0x1f);
Time=newtime;
}
```

Summarize

2017-2018-1 20155315 embedded C language test of the basic design of information security system