• State Not Answered
  • Locked Locked
  • Replies 8 replies
  • Subscribers 21 subscribers
  • Views 2797 views
  • Users 0 members are here
2025 survey

We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.

Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

How to use xdata?

Hsu YungSheng

Hi

This is code compiled with Keil C, but not working

#include <AT89X51.H>

xdata char Index _at_ 0x00;
void Clear_DDRAM(char index);

void main(void)
{
Clear_DDRAM(0x00);
while(1);
}

void Clear_DDRAM(char index)
{
int a;
for(a=0;a<65536;a++)
{
P3_4=0; //IOCS=0;
P3_1=0;
P3_0=0;
P1_0=0; //Reset=0;
Index=index;
P3_4=1; //IOCS=1;
Index=Index+a;
}
}

The xdata has 64K address range.
Here is my queation:
How to series to write data(0x00) into next address(Star address at 0x00). The assembly code is "INC DPTR" so have any instruction like it in keil C.

Parents
  • 0

    Hsu,

    I think people are having a hard time understanding your question. It looks like you are attempting to write a routine to initialize your xdata space. It looks like you want a function that will take a value passed in, and then write that value to every location in xdata. For instance, you want the call:

    Clear_DDRam(0x00)

    to fill the whole xdata address space with zeroes. Is that right? If so, your code is very confused. Maybe try something like this:

    void Fill_DDRAM(unsigned char value);

void main(void) {
   Fill_DDRAM(0x00);
   while(1);
}

void Fill_DDRAM(unsigned char value) {
   unsigned char xdata * data Index;
   int data loopcount;
   Index = 0x0000;
   P3_1 = 0;
   P3_0 = 0;
   P1_0 = 0;
   for (loopcount = 0; loopcount < 65535; loopcount++) {
      P3_4 = 0;
      *Index = value;
      P3_4 = 1;
      Index++;
   }
   *Index = value;  //Take care of last location
}

    Note that I've changed your loop. The loop as you wrote it is an infinite loop. An in will ALWAYS be less than 65536. I have changed my loop to "<65535" and then took care of the last location outside the loop. It's ugly, but you get the idea.

    Hope that helps.

Reply
  • 0

    Hsu,

    I think people are having a hard time understanding your question. It looks like you are attempting to write a routine to initialize your xdata space. It looks like you want a function that will take a value passed in, and then write that value to every location in xdata. For instance, you want the call:

    Clear_DDRam(0x00)

    to fill the whole xdata address space with zeroes. Is that right? If so, your code is very confused. Maybe try something like this:

    void Fill_DDRAM(unsigned char value);

void main(void) {
   Fill_DDRAM(0x00);
   while(1);
}

void Fill_DDRAM(unsigned char value) {
   unsigned char xdata * data Index;
   int data loopcount;
   Index = 0x0000;
   P3_1 = 0;
   P3_0 = 0;
   P1_0 = 0;
   for (loopcount = 0; loopcount < 65535; loopcount++) {
      P3_4 = 0;
      *Index = value;
      P3_4 = 1;
      Index++;
   }
   *Index = value;  //Take care of last location
}

    Note that I've changed your loop. The loop as you wrote it is an infinite loop. An in will ALWAYS be less than 65536. I have changed my loop to "<65535" and then took care of the last location outside the loop. It's ugly, but you get the idea.

    Hope that helps.

Children