12/14

ADDRESSING UP TO 4 MBYTES OF EXTERNAL MEMORY

3.4.4 Emulation

For emulation, during the down load of the application into the emulator, the access to the dy-

namic segments cannot be configured properly since the emulator is in reset state. To get

around this, we can use the internal memory of the emulator as a buffer and then transfer the

information from the emulator memory (declared as SYSTEM memory in the Mapfile of ST

Visual Debugger (STVD9) to the external memory (declared as USER memory in the Map file

of STVD9). This operation is done in the Start up file of the software example after the initiali-

zation of the external memory interface (if needed). It is done by the secinfo table. Refer to

GCC9 user manual for more information on the secinfo section.

By using this process, we need twice as much memory since any external memory needs to

have a buffer. Therefore the maximum amount of memory available during emulation is 2MB.

3.4.5 Capabilities and limitations

Due to the fact that dynamic segments can only be accessed one by one, some limitations

bilities and limitations.

Table 1. Software capabilities and limitations

Legend: SS = Static Segment, DS = Dynamic Segment.

Type of data

Location

Capability

Emulation

Code

Execution in SS or DS

Yes

OK

Jump or call from SS to DS

Yes

OK

Jump or call from DS to SS

Yes

OK

Jump or call from DS to another DS

NO

N/A

Jump or call from DS to the same DS

Yes

OK

Constant

Located in the SS and used by a program

in the SS or DS

Yes

Always seen

Located in the DS and used by a program

in the SS or the same DS as the constant

Yes

Not seen if the DS is

not selected

Located in the DS and used by a program

in another DS

No

N/A

Initialized variables

Located in the SS and used by a program

in the SS or DS

Yes

Always seen

Located in the DS and used by a program

in the SS or the same DS as the constant

Yes

Not seen if the DS is

not selected

Located in the DS and used by a program

in another DS

No

N/A

Un-initialized varia-

bles

Located in the SS and used by a program

in the SS or DS

Yes

Always seen

Located in the DS and used by a program

in the SS or the same DS as the constant

Yes

Not seen if the DS is

not selected

Located in the DS and used by a program

in another DS

No

N/A