I have a macro that I use with CBLOCK, which I find extremely helpful in
allocating the use of the extremely limited RAM in the PIC processors.

----------
The macro:
----------

UpdateRam   macro banktoupdate, lastused
RAMBASE#v(banktoupdate) set lastused+1
updateramtemp set RAMTOP#v(banktoupdate)-RAMBASE#v(banktoupdate)
   MESSG Ram bank #v(banktoupdate) after lastused: next =
#v(RAMBASE#v(banktoupdate)), left = #v(updateramtemp)
   endm  ;UpdateRam

-----------------------------------------
A few variables to be used by that macro:

Note: these are for 16F876,
change to suit processor being used...
-----------------------------------------

RAMBASE0   set   0x20
RAMBASE1   set   0xa0
RAMBASE2   set   0x110
RAMBASE3   set   0x190

RAMTOP0  set   0x70
RAMTOP1  set   0xe0
RAMTOP2  set   0x170
RAMTOP3  set   0x1f0


------------------------------------------------------------
A sample of using the macro to "declare" some RAM variables:
------------------------------------------------------------

;Most ISR variables are in bank 0
  cblock  RAMBASE0        ;Start letting assembler allocate bank 0 starting
here
          ISR_S_TMP
          ISR_PC_TMP
          ISR_FSR_TMP
   endc
   UpdateRam 0,ISR_FSR_TMP

----------------------------------------------------------------------------
---
When this is assembled, you get the following message in your assembler
output:
----------------------------------------------------------------------------
---

Message[301] C:\CODE\TIMKEN\MEMORY.INC 51 : MESSAGE: (Ram bank 0 after
ISR_FSR_TMP: next = 35, left = 77)

----------------------------------------------------------------------------
----------------------------
Somewhere near the end of your program, you can put this to automatically
check for overflowing the RAM:
----------------------------------------------------------------------------
----------------------------

 If ( RAMBASE0 > RAMTOP0)
 Error "Overflowed Bank 0 Register File"
 EndIf

 If ( RAMBASE1 > RAMTOP1)
 Error "Overflowed Bank 1 Register File"
 EndIf

 If ( RAMBASE2 > RAMTOP2)
 Error "Overflowed Bank 0 Register File"
 EndIf

 If ( RAMBASE3 > RAMTOP3)
 Error "Overflowed Bank 1 Register File"
 EndIf


----------------------------------------------------------------------------
-----------------------

I find that this helps make the primitive programming tools act somewhat
more like something civilized,
so that I can concentrate on the (still pretty painful) job of writing
assembly code for a machine that
combines in one processor all the worst memory-management schemes known to
programmers.

Now, mind you I like PIC's a lot for their price/performance, their
peripherals, and Microchip's company
philosophy, but I am getting pretty tired of programming them, and wish they
could plop a nicer CPU onto
those chips.

> -----Original Message-----
> From: Bob Ammerman [mailto:RAMMERMAN@PRODIGY.NET]
> Sent: Tuesday, May 29, 2001 6:29 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]:EQU and CBLOCK
>
>
> >         CBLOCK  0x021
> >         temp
> >         temp1
> >         .
> >         .
> >         .
> >         ;(and so on)
> >         zzzzzzzz        ;just a marker reg.
> >         ENDC
> >
> >         IF zzzzzzzz >= 0X070
> >         MESSG "BANK 0 IS FULL!!"
> >         ENDIF
> >
> > Quentin
>
> The test above should be:
>
>     If zzzzzzzz > 0x70
>
> It is ok for zzzzzzzz to be == 0x70.
>
> Bob Ammerman
> RAm Systems
> (contract development of high performance, high function, low-level
> software)
>
> --
> http://www.piclist.com hint: The PICList is archived three different
> ways.  See http://www.piclist.com/#archives for details.
>
>

--
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