Re: [Sdcc-user] Help with DSEG

[Jesus Calvino-F. <Je...@ec...>]

Hi Evandro,

The problem is that the sum of DSEG and OSEG must be less than 128 (0x80), 
otherwise variables will overflow and write to the sfr memory.  One quick 
fix for your problem would be to use some of the memory allocated for bit 
variables (BSEG, starting at address 0x20) which is available:

BSEG                               0000   000C =     12. bytes

By the way, it should read 12 bits not bytes.  Since 12 bits takes only two 
bytes, there are 14 extra bytes available for general use.  Therefore when 
linking you could use the option '--data-loc 0x22'.

Some time ago I encounter the same problem and after figuring out what was 
happening I wrote an small program called 'summary.c' which makes all the 
computations from the map file and warns if the numbers don't check.  You 
can get it from the archives:

http://www.geocrawler.com/archives/3/3278/2002/1/0/7559122/

Hope this helps.  Best regards,

Jesus

At 04:11 PM 8/25/02 -0300, EVANDRO LUIZ HAUENSTEIN wrote:
>Hi All,
>
>I have some problems with memory in my project (small model, target
>mcs51, 89C52).
>When the DSEG reaches around 75 bytes the program crashes...
>
>I notice that when these happens, the OSEG and SSEG goes to these
>addresses:
>OSEG                               007E   0004 =      4. bytes (REL,OVR)
>SSEG                               0082   0001 =      1. bytes (REL,CON)
>
>Whats Im doing wrong?
>
>In the example below, the program is still working. When I declare some
>DATA vars (or more functions) the DSEG segmente exceed that 75 bytes and
>nothing works anymore. Im checking the stack and it never exceeds the
>address 175 (my uC has 256bytes RAM).
>
>Part of Makefile
>/*******************************************************/
>SDCCCFLAGS = --model-small
>SDCCCFLAGS += -DSTACK_PROBE
>SDCCCFLAGS += --debug
>ASLINKFLAGS = --code-loc 0x2000 --data-loc 0x30 --stack-after-data
>--xram-loc 0x6000
>
>
>Part of MAP (working):
>/*******************************************************/
>Area                               Addr   Size   Decimal Bytes
>(Attributes)
>--------------------------------   ----   ----   ------- -----
>------------
>DSEG                               0030   0048 =     72. bytes (REL,CON)
>
>Area                               Addr   Size   Decimal Bytes
>(Attributes)
>--------------------------------   ----   ----   ------- -----
>------------
>OSEG                               0078   0004 =      4. bytes (REL,OVR)
>
>Area                               Addr   Size   Decimal Bytes
>(Attributes)
>--------------------------------   ----   ----   ------- -----
>------------
>SSEG                               007C   0001 =      1. bytes (REL,CON)
>
>Area                               Addr   Size   Decimal Bytes
>(Attributes)
>--------------------------------   ----   ----   ------- -----
>------------
>ISEG                               0080   0000 =      0. bytes (REL,CON)
>
>Area                               Addr   Size   Decimal Bytes
>(Attributes)
>--------------------------------   ----   ----   ------- -----
>------------
>BSEG                               0000   000C =     12. bytes
>(REL,CON,BIT)
>
>Area                               Addr   Size   Decimal Bytes
>(Attributes)
>--------------------------------   ----   ----   ------- -----
>------------
>XSEG                               6000   007C =    124. bytes
>(REL,CON,XDATA)
>
>Area                               Addr   Size   Decimal Bytes
>(Attributes)
>--------------------------------   ----   ----   ------- -----
>------------
>XISEG                              607C   0000 =      0. bytes
>(REL,CON,XDATA)
>
>Area                               Addr   Size   Decimal Bytes
>(Attributes)
>--------------------------------   ----   ----   ------- -----
>------------
>CSEG                               2000   1D2D =   7469. bytes
>(REL,CON,CODE)
>
>Area                               Addr   Size   Decimal Bytes
>(Attributes)
>--------------------------------   ----   ----   ------- -----
>------------
>GSINIT                             3D2D   005F =     95. bytes
>(REL,CON,CODE)
>
>Area                               Addr   Size   Decimal Bytes
>(Attributes)
>--------------------------------   ----   ----   ------- -----
>------------
>GSFINAL                            3D8C   0003 =      3. bytes
>(REL,CON,CODE)
>       Value  Global
>    --------  --------------------------------
>   0C:3D8C    A$main$314
>
>Area                               Addr   Size   Decimal Bytes
>(Attributes)
>--------------------------------   ----   ----   ------- -----
>------------
>HOME                               3D8F   0000 =      0. bytes
>(REL,CON,CODE)
>
>Area                               Addr   Size   Decimal Bytes
>(Attributes)
>--------------------------------   ----   ----   ------- -----
>------------
>XINIT                              3D8F   0000 =      0. bytes
>(REL,CON,CODE)
>
>/*******************************************************/
>CSEG = 0x2000
>DSEG = 0x0030
>XSEG = 0x6000
>ISEG = 0x0080
>BSEG = 0x0000
>
>/*******************************************************/
>
>
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