TMS320F2809: Logic of compiler/linker for global variable with size 32 and 33

Wayne Huang

Part Number: TMS320F2809
Other Parts Discussed in Thread: TEST2

Tool/software:

Hi champs,

I am asking this for our customer.

The user finds the RAM size allocated for global variables (that is .ebss) seems to increase a lot when size increase over 32.

That is,

#define SIZE 33

uint16_t test1[SIZE]

uint16_t test2[SIZE]

uint16_t test3[SIZE]

......

.ebss increase linearly when SIZE increases below 32, say 30, 31, 32.

.ebss increase linearly when SIZE increases over 32, say 32, 33, 34.

But it seems .ebss increase a lot when SIZE is changed from 32 to 33.

Questions:

1. Does it make sense for our compiler/linker?

2. Can the user avoid this and/or optimize .ebss allocation size if the user has to use SIZE 33?

over 1 year ago

0 Torsten Robitzki over 1 year ago

Expert 2474 points

Hi,

how are you measuring the size? I did a quick test in a f280049 project, and the size was growing linear in my example (data taken from the map file:

0000001f     main.c.obj (.ebss:_test1)
00000020     main.c.obj (.ebss:_test2)
00000021     main.c.obj (.ebss:_test3)
00000022     main.c.obj (.ebss:_test4)
00000023     main.c.obj (.ebss:_test5)

That's the code:

#define SIZE 31

uint16_t test1[SIZE];

uint16_t test2[SIZE+1];

uint16_t test3[SIZE+2];

uint16_t test4[SIZE+3];

uint16_t test5[SIZE+4];

+1 George Mock over 1 year ago

TI__Guru**** 251100 points

Please see the article Data blocking in the C2000 MCU compiler explained. Therefore, a possible workaround is to apply __attribute__((noblocked)) to the problem arrays.

Thanks and regards,

-George

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F2809: Logic of compiler/linker for global variable with size 32 and 33