Atmel CAVR-4 Manual De Usuario

CAVR-4

Placing segments in memory

Reference Guide

See the IAR Linker and Library Tools Reference Guide for more details.

Use the -Z command when you need to keep a segment in one consecutive chunk, when 
you need to preserve the order of segment parts in a segment, or, more unlikely, when 
you need to put segments in a specific order.

The following illustrates how to use the 

-Z

 command to place the segment 

MYSEGMENTA

 

followed by the segment 

MYSEGMENTB

 in 

DATA

 memory (that is, external RAM) in the 

memory range 

0x1000-0xCFFF

.

-Z(DATA)MYSEGMENTA,MYSEGMENTB=1000-CFFF

Two segments of different types can be placed in the same memory area by not 
specifying a range for the second segment. In the following example, the 

MYSEGMENTA

 

segment is first located in memory. Then, the rest of the memory range could be used by 

MYCODE

.

-Z(DATA)MYSEGMENTA=1000-CFFF

-Z(CODE)MYCODE

Two memory ranges may overlap. This allows segments with different placement 
requirements to share parts of the memory space; for example:

-Z(DATA)MYSMALLSEGMENT=1000-20FF

-Z(DATA)MYLARGESEGMENT=1000-CFFF

Even though it is not strictly required, make sure to always specify the end of each 
memory range. If you do this, the IAR XLINK Linker will alert you if your segments do 
not fit in the specified ranges.

The 

-P

 command differs from 

-Z

 in that it does not necessarily place the segments (or 

segment parts) sequentially. With 

-P

 it is possible to put segment parts into holes left by 

earlier placements.

The following example illustrates how the XLINK 

-P

 option can be used for making 

efficient use of the memory area. The command will place the data segment 

MYDATA

 in 

DATA memory (that is, in RAM) in the memory range:

-P(DATA)MYDATA=0-FFF,1000-1FFF

If your application has an additional RAM area in the memory range 

0xF000-0xF7FF

, 

you just add that to the original definition:

-P(DATA)MYDATA=0-FFF,1000

–1FFF,F000-F7FF