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max size of an array in rom ?

 
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JM35



Joined: 10 Feb 2009
Posts: 10

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max size of an array in rom ?
PostPosted: Wed Mar 04, 2009 12:22 pm     Reply with quote
I use a 16f877 for driving a 128*64 LCD.
I need a table of 475 bytes i wish, of course, to place in rom for saving ram

Code:

const int8 ascii[] =   {
         0x0,0x0,0x0,0x0,0x0,           //    32 -esp- 20               
         0x0,0x0,0x4F,0x0,0x0,          //   33 - ! - 21
         0x0,0x7,0x0,0x7,0x0,          //   34 - " - 22
         0x14,0x7F,0x14,0x7F,0x14,       //   35 - # - 23
         0x24,0x2A,0x7F,0x2A,0x12,       //   36 - $ - 24
         0x23,0x13,0x8,0x64,0x62,       //   37 - % - 25
         0x36,0x49,0x55,0x22,0x50,       //   38 - & - 26
         0x0,0x5,0x3,0x0,0x0,          //   39 - ' - 27
         0x1C,0x22,0x41,0x0,0x0,       //   40 - ( - 28
         0x0,0x0,0x41,0x22,0x1C,       //   41 - ) - 29
         0x14,0x8,0x3E,0x8,0x14,       //   42 - * - 2A
         0x8,0x8,0x3E,0x8,0x8,          //   43 - + - 2B
         0x0,0x50,0x30,0x0,0x0,          //   44 - , - 2C
         0x8,0x8,0x8,0x8,0x8,          //   45 - - - 2D
         0x0,0x60,0x60,0x0,0x0,          //   46 - . - 2E
         0x20,0x10,0x8,0x4,0x2,          //   47 - / - 2F
         0x3E,0x51,0x49,0x45,0x3E,       //   48 - 0 - 30
         0x0,0x42,0x7F,0x40,0x0,       //   49 - 1 - 31
         0x42,0x61,0x51,0x49,0x46,       //   50 - 2 - 32
         0x21,0x41,0x45,0x4B,0x31,       //   51 - 3 - 33
         0x18,0x14,0x12,0x7F,0x10,       //   52 - 4 - 34
         0x27,0x45,0x45,0x45,0x39,       //   53 - 5 - 35
         0x3C,0x4A,0x49,0x49,0x30,       //   54 - 6 - 36
         0x1,0x71,0x9,0x5,0x3,          //   55 - 7 - 37
         0x36,0x49,0x49,0x49,0x36,       //   56 - 8 - 38
         0x06,0x49,0x49,0x29,0x1E,       //   57 - 9 - 39   
         0x0,0x36,0x36,0x0,0x0,          //   58 - : - 3A
         0x0,0x56,0x36,0x0,0x0,          //   59 - ; - 3B
         0x8,0x14,0x22,0x41,0x0,       //   60 - < - 3C
         0x14,0x14,0x14,0x14,0x14,       //   61 - = - 3D
         0x0,0x41,0x22,0x14,0x8,       //   62 - > - 3E
         0x2,0x1,0x51,0x9,0x6,          //   63 - ? - 3F
         0x32,0x49,0x79,0x41,0x3E,       //   64 - @ - 40
         0x7E,0x11,0x11,0x11,0x7E,       //   65 - A - 41
         0x7F,0x49,0x49,0x49,0x36,       //   66 - B - 42
         0x3E,0x41,0x41,0x41,0x22,       //   67 - C - 43
         0x7F,0x41,0x41,0x22,0x1C,       //   68 - D - 44
         0x7F,0x49,0x49,0x49,0x41,       //   69 - E - 45
         0x7F,0x9,0x9,0x9,0x1,          //   70 - F - 46
         0x3E,0x41,0x49,0x49,0x7A,       //   71 - G - 47
         0x7F,0x8,0x8,0x8,0x7F,          //   72 - H - 48
         0x0,0x41,0x7F,0x41,0x0,       //   73 - I - 49
         0x20,0x40,0x41,0x3F,0x1,       //   74 - J - 4A
         0x7F,0x8,0x14,0x22,0x41,       //   75 - K - 4B
         0x7F,0x40,0x40,0x40,0x40,       //   76 - L - 4C
         0x7F,0x2,0xC,0x2,0x7F,          //   77 - M - 4D
         0x7F,0x4,0x8,0x10,0x7F,       //   78 - N - 4E
         0x3E,0x41,0x41,0x41,0x3E,       //   79 - O - 4F
         0x7F,0x9,0x9,0x9,0x6,         //   80 - P - 50
         0x3E,0x41,0x51,0x21,0x5E,       //   81 - Q - 51
         0x7F,0x9,0x19,0x29,0x46,       //   82 - R - 52
         0x46,0x49,0x49,0x49,0x31,       //   83 - S - 53
         0x1,0x1,0x7F,0x1,0x1,          //   84 - T - 54
         0x3F,0x40,0x40,0x40,0x3F,       //   85 - U - 55
         0x1F,0x20,0x40,0x20,0x1F,       //   86 - V - 56
         0x3F,0x40,0x38,0x40,0x3F,       //   87 - W - 57
         0x63,0x14,0x8,0x14,0x63,       //   88 - X - 58
         0x7,0x8,0x70,0x8,0x7,          //   89 - Y - 59
         0x61,0x51,0x49,0x45,0x43,       //   90 - Z - 5A
         0x7F,0x41,0x41,0x0,0x0,       //   91 - [ - 5B
         0x2,0x4,0x8,0x10,0x20,          //   92 - \ - 5C
         0x0,0x0,0x41,0x41,0x7F,       //   93 - ] - 5D
         0x4,0x2,0x1,0x2,0x4,          //   94 - ^ - 5E
         0x40,0x40,0x40,0x40,0x40,       //   95 - _ - 5F
         0x0,0x1,0x2,0x4,0x0,          //   96 - ` - 60
         0x20,0x54,0x54,0x54,0x78,      //   97 - a - 61
         0x7F,0x48,0x44,0x44,0x38,       //   98 - b - 62
         0x38,0x44,0x44,0x44,0x20,       //   99 - c - 63
         0x38,0x44,0x44,0x48,0x7F,       //   100  d - 64
         0x38,0x54,0x54,0x54,0x18,       //   101  e - 65
         0x8,0x7E,0x9,0x1,0x2,          //   102  f - 66
         0xC,0x52,0x52,0x52,0x3E,       //   103  g - 67
         0x7F,0x8,0x4,0x4,0x78,          //   104  h - 68
         0x0,0x44,0x7D,0x40,0x0,       //   105  i - 69
         0x0,0x20,0x40,0x44,0x3D,       //   106  j - 6A
         0x7F,0x10,0x28,0x44,0x0,       //   107  k - 6B
         0x0,0x41,0x7F,0x40,0x0,       //   108  l - 6C
         0x7C,0x4,0x18,0x4,0x78,       //   109  m - 6D
         0x7C,0x8,0x4,0x4,0x78,          //   110  n - 6E
         0x38,0x44,0x44,0x44,0x38,       //   111  o - 6F
         0x7C,0x14,0x14,0x14,0x8,       //   112  p - 70
         0x8,0x14,0x14,0x18,0x7C,       //   113  q - 71
         0x7C,0x8,0x4,0x4,0x8,          //    114  r - 72
         0x48,0x54,0x54,0x54,0x20,       //   115  s - 73
         0x4,0x3F,0x44,0x40,0x20,       //   116  t - 74
         0x3C,0x40,0x40,0x20,0x7C,       //   117  u - 75
         0x1C,0x20,0x40,0x20,0x1C,       //   118  v - 76
         0x3C,0x40,0x30,0x40,0x3C,       //   119  w - 77
         0x44,0x28,0x10,0x28,0x44,       //   120  x - 78
         0xC,0x50,0x50,0x50,0x3C,       //   121  y - 79
         0x44,0x64,0x54,0x4C,0x44,       //   122  z - 7A
         0x8,0x36,0x41,0x0,0x0,          //   123  { - 7B
         0x0,0x0,0x7F,0x0,0x0,          //   124  | - 7C
         0x0,0x0,0x41,0x36,0x8,          //   125  } - 7D
         0x0,0x8,0x4,0x8,0x4         //    126  ~ - 7E     
};


here's the function for accessing the character :

Code:

void lcd_putchar(unsigned char c){
   // FONT_MIN = 32 -esp- 20           // 5 octets par caractère
   // FONT_MAX = 126  ~ - 7E       
   unsigned char cpt;
   unsigned int16 index;
   if ((c<32)||(c>126)) c='?'; 
   (char)c=(char)c-32;
   index = (long)c*5;             // *5=*(4+1)= <<2 +1
   for(cpt=5; cpt>0; cpt--){
      lcd_putdata(ascii[index++]);
      lcd_compteur();
   }
   lcd_putdata(0);                     // 1 colonne vide (espace inter caractères)
   lcd_compteur();
}


It don't work with CCS PCM C Compiler, Version 4.073, why ?

The code is OK with Hi-Tech compiler ...

Thank's !
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Mar 04, 2009 12:30 pm     Reply with quote
For 16F, there is a 256 byte limit for 'const' arrays. For 18F, this limit
doesn't exist. For 16F, you will need to split up a large ROM array into
two or more smaller arrays.
http://www.ccsinfo.com/forum/viewtopic.php?t=33085&start=4
JM35



Joined: 10 Feb 2009
Posts: 10

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PostPosted: Wed Mar 04, 2009 12:34 pm     Reply with quote
Ok thanks ... crappy limitation of this compiler.

So i have to upgrade to 18F.
JM35



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PostPosted: Wed Mar 04, 2009 12:37 pm     Reply with quote
I spent hours with this problem, because compiler do not signal error or warning about this ! So I suggest a improvment for next version ...
Thank's for your help.
treitmey



Joined: 23 Jan 2004
Posts: 1094
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PostPosted: Wed Mar 04, 2009 1:09 pm     Reply with quote
Quote:
Ok thanks ... crappy limitation of this compiler.

Its not the compiler, its the design of the hardware.

If the compiler took care of it for you... The asm would end up
looking just like if you simply split up the array yourself.

Try it. It's not too hard.
FvM



Joined: 27 Aug 2008
Posts: 2337
Location: Germany

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PostPosted: Wed Mar 04, 2009 1:47 pm     Reply with quote
Quote:
Its not the compiler, its the design of the hardware.
I don't agree in this case. PIC16F instruction set allows to read arbitrary program memory locations addressed by a pointer, it can be simply translated to EEADRH and EEADRL, a code example is shown in the datasheet. Built-in read_program_memory() should also do, but I didn't try.
Ttelmah
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PostPosted: Wed Mar 04, 2009 3:33 pm     Reply with quote
The problem is that most 16 chips don't support this.

You can put your large array into the memory, and access it on the ones that do, by using a #ROM statement, and accessing it with a read_program_memory function.
With a couple of macros to handle row/column address calculations, it is almost as simple as a normal array access.
The CCS approach works on all 16 chips, which is why they went this way.

Best Wishes
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