'reserving' memory space

[comwarrior]

I want to 'reserve' a fixed chunk of program memory so that I can load code from a serial eeprom... proberbly a similar thing to a boot loader...

I was thinking of using the assembler ORG command but i was wondering if their was a spacific way of doing it in picbasic?

What aproches do people use?

Thanks

[mackrackit]

Something like this?
http://www.picbasic.co.uk/forum/show...ght=playground

[Melanie]

I find this quite useful - especially in PICs which have insufficient EEPROM for my needs...

	'
	'	Executable Program Starts Here
	'	==============================
	goto JumpStart

	'
	'	System References
	'	================

		'
		'	SETUPs
		'	------
Setups:
	ASM

	db	0xA4,0xA5,0xB0,0xB1,0xB2,0xB3,0xB4,0xD0	;  00-07
	db	0xD1,0xD2,0xD5,0xD6,0xD9,0xDA,0xDD,0xDE ;  08-15
	db	0xE1,0xE2,0xE5,0xE6,0xE7,0xE8,0xE9,0xEA ;  16-23
	db	0xEB,0xEC,0xED,0xEE,0xF0,0xF1,0xF2,0xF4 ;  24-31
	db	0xFA,0xF9,0xEF,0x00,0x00,0x00,0x00,0x00 ;  32-39
	db	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 ;  40-47
	db	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 ;  48-55
	db	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 ;  56-63
	db	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 ;  64-71
	db	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 ;  72-79
	db	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 ;  80-87
	db	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 ;  88-95
	db	0xB5,0xB6,0xB7,0xB8,0xB9,0xBA,0x00,0x00 ;  96-103
	db	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 ; 104-111
	db	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 ; 112-119
	db	0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 ; 120-127

	ENDASM

JumpStart:

Now, you can reserve as little or as much Programspace as you want and PICBasic takes care of everything else. The most I'd ever done was 8kB, but it sure is handy (and saves on having an external EEPROM). Just remember how much you've allocated and never to do write operations outside of your allocated space (otherwise you'll corrupt your own program).

This is a great way for long-term but occasional Data-Logging (like the Plastic Chickens you have in your industrial Fridge or Freezers) as you really minimalise your parts count.

[comwarrior]

hmmm, interesting...
I'm assuming i can then use ORG to position it in memory?

Thanks mel

[Melanie]

Actually I don't do that, because I prefer PBP to position it's internals for itself. If you start using ORG then you could, potentially, run the risk of having PBP create code that could intrude into your reserved space. All I do is workout the address of the start Label (in my previous example 'Setups:') and reference everything from that starting point. The added advantage is that all the reports for BYTE or WORD usage for your PIC take into account your Reserved Space and you get a better feel for how you're filling your PIC up. If you decide you are going to use ORG and position your reserved space up in high memory (nothing stopping you doing that), then you don't get a clear idea of how big your PBP code is, and how much you've got vacant before you intrude into your reserved space.

And before you turn around and ask "How can I work out how to get the address of a Label?", let me refer you to a three-year-old thread...

http://www.picbasic.co.uk/forum/showthread.php?t=3881

[comwarrior]

ok, going to have to come clean...

the reason i want to block off some memory addresses is because one of my original PIC's (877A) has faulty memory locations due to a slight power surge and brownout while being programed... yes, my PC PSU was wrecked... luckerly the only other damage was my graphics card...

i have a low level, really basic task for it to do, if i can get the program to skip the affected memory locations...

The blocks are...

0x0008 to 0x003F
0x0108 to 0x013F
0x0208 to 0x023F
0x0308 to 0x033F
0x0408 to 0x043F
0x0508 to 0x053F
0x0608 to 0x063F
0x0708 to 0x073F

Anyone see a paturn?... lol

the thaught occured to me to alter the ASM so that the memory table thing....

RAM_START       		EQU	00020h
RAM_END         		EQU	001EFh
RAM_BANKS       		EQU	00004h
BANK0_START     		EQU	00020h
BANK0_END       		EQU	0007Fh
BANK1_START     		EQU	000A0h
BANK1_END       		EQU	000EFh
BANK2_START     		EQU	00110h
BANK2_END       		EQU	0016Fh
BANK3_START     		EQU	00190h
BANK3_END       		EQU	001EFh
EEPROM_START    		EQU	02100h
EEPROM_END      		EQU	021FFh

avoides the faulty locations and recompile it using mplabs compiler...

But then i realised it wasn't going to be that easy...

:edit
Having said that... i could alter EEPROM_START to after the first bad block, manually insert a jump followed by enough 3FFF's, and hope the program fits in befor the seconds one (unlikely)...