Syntax

region-operand 
 | region-expr | region-operand 
 | region-expr - region-operand 
 | region-expr & region-operand 

where region-operand is one of:

( region-expr )
region-name
region-literal
empty-region

where region-name is a region, see define region directive

where region-literal is a region literal, see Region literal

and where empty-region is an empty region, see Empty region.

Description

Normally, a region consists of one memory range, which means a region literal is sufficient to express it. When a region contains several ranges, possibly in different memories, it is instead necessary to use a region expression to express it. Region expressions are actually set expressions on sets of memory ranges.

To create region expressions, three operators are available: union (|), intersection (&), and difference (-). These operators work as in set theory. For example, if you have the sets A and B, then the result of the operators would be:

Example

/* Resulting in a range starting at 1000 and ending at 2FFF, in memory Mem */
Mem:[from 0x1000 to 0x1FFF]
| Mem:[from 0x1500 to 0x2FFF]

/* Resulting in a range starting at 1500 and ending at 1FFF, in memory Mem */
Mem:[from 0x1000 to 0x1FFF]
& Mem:[from 0x1500 to 0x2FFF]

/* Resulting in a range starting at 1000 and ending at 14FF, in memory Mem */
Mem:[from 0x1000 to 0x1FFF]
- Mem:[from 0x1500 to 0x2FFF]

/* Resulting in two ranges, the first starting at 1000 and ending at 1FFF, the
second starting at 2501 and ending at 2FFF. Both located in memory Mem */
Mem:[from 0x1000 to 0x2FFF]
- Mem:[from 0x2000 to 0x24FF]