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How do I #locate a 2-D array

 
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treitmey



Joined: 23 Jan 2004
Posts: 1094
Location: Appleton,WI USA

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How do I #locate a 2-D array
PostPosted: Wed Nov 10, 2004 5:52 pm     Reply with quote
Compiler 3.212
16F877 @ 16MhZ
i want to #locate the different parts of a 2-d array.
can this be done?

Code:
int8 table[4][25];
#locate table[0]=0x110
#locate table[1]=0x129
#locate table[2]=0x190
#locate table[3]=0x1A9


so that each of the four is able to fit in the ram page.

Thanks in advace for any help.
tjr
Haplo



Joined: 06 Sep 2003
Posts: 659
Location: Sydney, Australia

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PostPosted: Wed Nov 10, 2004 5:59 pm     Reply with quote
No you can't break an array like that. And too be sure I tried it and the compiler returns an error.

One way to do this is to define 4 separate arrays, and then write wrapper functions (with two parameters) for accessing them.
treitmey



Joined: 23 Jan 2004
Posts: 1094
Location: Appleton,WI USA

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PostPosted: Thu Nov 11, 2004 8:44 am     Reply with quote
I understand the 4 arrays. But how are the wrapper functions made. What are they suppose to do? Are they to FAKE out program, to make it look like i'm using a 2-d array?


Code:
int8 table0[24];
int8 table1[24];
int8 table2[24];
int8 table3[24];
// and #locate if need be.

FAKEOUT(param1,param2)
{
  //
  //
  //
}


I was thinking that with the 4 arrays, I could have an array of pointers to them. Then I could pass these to the function. Is that where you were going. In effect a 4 ellement array of pointers to 4 arrays.

THANKS FOR THE RESPONSE
tjr
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Nov 11, 2004 12:40 pm     Reply with quote
Here is one example that I did in the past. It possibly could be
re-written in a more efficient way, but this example will give you
the main idea.
Code:

// bigarray.c
// This program shows how to make "wrapper" functions
// to allow access to an array larger than one ram bank.

//------------------------------------------------------
// INCLUDE FILES

#include "16F877.h"
#device *=16

//-------------------------------------------------------
// COMPILER AND CHIP CONFIGURATION DIRECTIVES

#fuses XT, NOWDT, NOPROTECT, PUT, BROWNOUT, NOLVP
#use Delay(Clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7)
#zero_ram

//-------------------------------------------------------
// DEFINITIONS

#define ARRAY_1_SIZE  80
#define ARRAY_2_SIZE  80

#define TOTAL_ARRAY_SIZE (ARRAY_1_SIZE + ARRAY_2_SIZE)

//-------------------------------------------------------
// GLOBALS

char array_1[ARRAY_1_SIZE];
char array_2[ARRAY_2_SIZE];

//-------------------------------------------------------
// FUNCTION PROTOTYPES

char read_big_array(char index);
void write_big_array(char index, char value);


//================================
main()
{
char i;
char temp;

printf("Start test\n\r");

// To test the functions, we will fill the big array
// with numbers equal to the index.

for(i = 0; i < TOTAL_ARRAY_SIZE; i++)
   {
    write_big_array(i, i);
   }

//----------------------------
// Now read them back and check the results.

for(i = 0; i < TOTAL_ARRAY_SIZE; i++)
   {
    temp = read_big_array(i);

    if(temp != i)
       printf("Error:  Address %02x, Wrote %02x, Read %02x\n\r", i, i, temp);
   }

//----------------------------


printf("Test done");

while(1);
}

//=================================
// This function reads a byte from the specified index.

char read_big_array(char index)
{
char retval;

if(index < ARRAY_1_SIZE)   // Is index within 1st array ?
  {
   retval = array_1[index]; 
  }     
else if(index < TOTAL_ARRAY_SIZE)  // Is index within 2nd array ?
  {
   index -= ARRAY_1_SIZE;  // Then adjust index so it's within array 2.
   retval = array_2[index];
  }
else  // If not in either array, then return zero.  (We have to return something).
  {
   retval = 0;
  }

return(retval);
}

//------------------------------------------
// This function writes a byte to the specified index.

void write_big_array(char index, char value)
{

if(index >= TOTAL_ARRAY_SIZE)  // Don't allow writing outside of the array limits
   return;

if(index < ARRAY_1_SIZE)    // Is the index within array 1 ?
   {
   array_1[index] = value;
  }     
else         // If not, it must be within array 2. 
  {
   index -= ARRAY_1_SIZE;   // Adjust the index so it's within array 2.
   array_2[index] = value;
  }

}
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