gnupic: address space
Subject:
Re: address space
From:
Maxime Larocque ####@####.####
Date:
10 Dec 2004 02:13:25 +0000
Message-Id: <41B905FE.6090402@yahoo.ca>
Hello,
Dante wrote:
> Ok, so I think perhaps this time I am using the proper forum for this
> question.
>
> I am using gpasm-0.12.4 (beta as per debian) I am attempting to use
> the variable directive to set up the variable labels to make life a
> wee bit easier. My own (and very limited experience) indicates that
> this should assign data address space for the variable. However
> looking at the symbols for the resulting code file seems to indicate
> that this is not really the case. It looks like attempting to <label>
> = (value); results in (value) being assigned as an address. This being
> the case, is there a way to assign both the address and a value, or do
> I need to do this a two seperat operations, or am I just being stupid?
>
> Keith
>
I was browsing the gputils manual about this.
Chapter 2 talks about a VARIABLE directive that does just that, but it
is about gpal. I does know much about gpal.
Chapter 3 talks about another VARIABLE directive, but this time for
assembler. This one is similar to CONSTANT, but is variable only at
compilation time, not runtime.
If that can help, I use the following macros in all my asm PIC projects
since maybe 2000:
===================== Code snipplet start
if PIC_FAMILY==16870
#define MAXLIB_MEMSTART_B0 0x020 ; 80 bytes + 16 shared
#define MAXLIB_MEMSTART_B1 0x0A0 ; 80 bytes
#define MAXLIB_MEMSTART_B2 0x110 ; 96 bytes
#define MAXLIB_MEMSTART_B3 0x190 ; 96 bytes
endif
if PIC_FAMILY==16628
#define MAXLIB_MEMSTART_B0 0x020 ; 80 bytes + 16 shared
#define MAXLIB_MEMLEN_B0 0x060
#define MAXLIB_MEMSTART_B1 0x0A0 ; 80 bytes
#define MAXLIB_MEMLEN_B1 0x050
#define MAXLIB_MEMSTART_B2 0x120 ; 48 bytes
#define MAXLIB_MEMLEN_B2 0x030
#define MAXLIB_MEMEND_B2 0x150
; No bank 3 in the pic16f628.
endif
; Dynamic variable allocation
; start of available memory
dec_var_count set MAXLIB_MEMSTART_B0
dec_var macro VARNAME
VARNAME set dec_var_count
dec_var_count set dec_var_count+1
if (dec_var_count == 0x71)
too_much_variables_bank0
endif
endm
===================== Code snipplet end
You just have to declaration actual RAM variable by using the macro:
dec_var A_RAM_VARIABLE
... and then use it in your software:
movfw A_RAM_VARIABLE
incf A_RAM_VARIABLE,f
etc...
I found it very usefull to develop modular software, since adding /
removing module does not imply reassigning all the data memory.
Hope that help.
Maxime Larocque
(Sorry about the library name, it's just a lack of imagination!)
