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Guest
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| large memory model with PIC18F6722 |
 Posted: Mon Jul 21, 2008 12:17 pm |
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Hello,
I have not been able to find any mention of how to specify either far pointers (24-bit) or how to enable the large memory model (where pointers are 24-bit by default) in the PCH compiler's manual or in this forum. Hopefully, I have just missed something obvious. 
I am using PCH Compiler v4.055 and my uC is the PIC18F6722. This PIC has 128 KiB of Program Flash (0x00000 - 0x1FFFF).
So far, I have not been able to determine how to place anything in the second 64 KiB of the Program Flash since it requires a 17th bit of addressing. And, from my testing, it appears that generated code also does not get placed in that address range.
My problem is that I have a large number of fonts and images that my application requires and I am currently right on the edge of 50% usage of the Program Flash. Minor changes like adding a simple printf() are now causing my application to fail to build with errors indicating lack of space. This is very annoying since I have a large amount of unused capacity just sitting there.
Any suggestions or guidance would be greatly appreciated.
Cheers,
James |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Jul 21, 2008 1:15 pm |
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Are you using #org statements for the fonts, etc. ?
If so, post some of them. |
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Guest
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| Posted: Mon Jul 21, 2008 1:26 pm |
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Here are a few characters from the small font set. All of the fonts and images use the same technique to load them into memory from a header file.
/* A */
#ROM 0x0d1f0={0x0000, 0x0f00, 0x00ff, 0x00f0, 0xfff0, 0xf0ff, 0x00f0, 0xf0f0, 0xf000, 0x0000, 0x0000}
/* B */
#ROM 0x0d1d8={0x0000, 0xff00, 0x00ff, 0x00f0, 0xfff0, 0x00ff, 0x00f0, 0xfff0, 0x00ff, 0x0000, 0x0000}
/* C */
#ROM 0x0d1c0={0x0000, 0x0f00, 0xf0ff, 0x00f0, 0xf000, 0x0000, 0x00f0, 0x0f00, 0xf0ff, 0x0000, 0x0000}
/* D */
#ROM 0x0d1a8={0x0000, 0xff00, 0x00ff, 0x00f0, 0xf0f0, 0xf000, 0x00f0, 0xfff0, 0x00ff, 0x0000, 0x0000} |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Jul 21, 2008 2:29 pm |
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I made a little test program and I blocked the compiler from using the
first 64K of the flash with an #org statement.
| Code: | #include <18F6722.h>
#fuses XT, NOWDT, PUT, BROWNOUT, NOLVP
#use delay(clock=4000000)
#org 0x0008, 0xFFFE {}
//=============================
void main(void)
{
while(1);
} |
Here's the .LST file for it, and it's using the upper 64K with
no problem. This test was done with your version, 4.055.
I stepped through the .LST file code with the MPLAB simulator
and it steps OK. Your contention is that the compiler is not
using the upper 64K, but based on this test, it will use it.
| Code: | 00000: GOTO 10000
....................
.................... #org 0x0008, 0xFFFE {}
....................
.................... void main(void)
.................... {
10000: CLRF FF8
10002: BCF FD0.7
10004: CLRF FEA
10006: CLRF FE9
10008: MOVF FC1,W
1000A: ANDLW C0
1000C: IORLW 0F
1000E: MOVWF FC1
10010: MOVLW 07
10012: MOVWF FB4
....................
....................
.................... while(1);
10014: GOTO 10014
.................... } |
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