Engineer To Engineer Note EE-62 a
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1. Engineer To Engineer Note FE 62 Technical Notes on using Analog Devices DSP components and development tools Phone 800 ANALOG D FAX 781 461 3010 EMAIL dsp support analog com FTP ftp analog com WEB www analog com dsp Copyright 1999 Analog Devices Inc All rights reserved Analog Devices assumes no responsibility for customer product design or the use or application of customers products or for any infringements of patents or rights of others which may result from Analog Devices assistance All trademarks and logos are property of their respective holders Information furnished by Analog Devices Applications and Development Tools Engineers is believed to be accurate and reliable however no responsibility is assumed by Analog Devices regarding the technical accuracy of the content provided in all Analog Devices Engineer to Engineer Notes Accessing Short Word Memory In C Last modified July 20 1999 Introduction The ADSP 2106x SHARC family processors C runtime environment natively processes 32 bit datatypes The DSP hardware can be configured to process 48 40 32 and 16 bit data although the C runtime environment only natively deals with 32 bit data This EE note will explain how to place variables and other datatypes into 16 bit or short word memory to allow for a more efficient use of memory and allows for tighter granularity of the data as well As mentioned earlier short word memory addressing is u2. IN 0x00030000 END 0x00033fff PM WIDTH 48 alt_pmco SEGMENT RAM BEGIN 0x00036000 END 0x00037fff DM WIDTH 32 seg_dmda SEGMENT RAM BEGIN 0x00038000 END 0x00039fff DM WIDTH 32 cheap seg_heap SEGMENT RAM BEGIN 0x0003a000 END 0x0003dfff DM WIDTH 32 seg_stak SEGMENT RAM BEGIN 0x0007c000 END 0x0007ffff DM WIDTH 16 alt_dmda ENDCVC Example Architecture File for v3 3 Development Tools g21k main c c a 21060c ach save temps g g21k short 33 c c mpmdata alt_dmda a 21060c ach save temps g g21k main o short 33 0 a 21060c ach o short 33 exe map g save temps Example batch file for v3 3 development tools Here we see from the above batch file that the build process must be performed in multiple stages The code and data segments that are to reside in alternate memory segments other than the default seg_pmco and seg_dmda segments must be compiled and linked separately The use of the c compiler switch stops the compiler before the linking stage for each source file Also note the use of the mpmdata compiler switch which tells the linker which alternate segment this code module will reside For more information please refer to pages 3 8 and 3 9 of the ADSP 21000 Family C Tools Manual third edition EE 62 Page 7 Notes on using Analog Devices DSP components and development tools Phone 800 ANALOG D FAX 781 461 3010 EMAIL dsp support analog com FTP ftp analog com Main c Short W
3. M RAM START 0x00021800 END 0x00025fff WIDTH 48 alt_pmco TYPE PM RAM START 0x00030000 END 0x00033fff WIDTH 48 seg_dmda TYPE DM RAM START 0x00036000 END 0x00037fff WIDTH 32 seg_heap TYPE DM RAM START 0x00038000 END 0x00039fff WIDTH 32 seg_stak TYPE DM RAM START 0x0003a000 END 0x0003dfff WIDTH 32 alt_dmda TYPE DM RAM START 0x0007c000 END 0x0007ffff WIDTH 16 PROCESSOR p0 LINK_AGAINST COMMAND_LINE_LINK_AGAINST OUTPUT COMMAND_LINE_OUTPUT_FILE SECTIONS text output section seg_rth INPUT SECTIONS OBIECTS seo rth IIRRARIFS seo rth EE 62 Page 3 Notes on using Analog Devices DSP components and development tools Phone 800 ANALOG D FAX 781 461 3010 EMAIL dsp support analog com FTP ftp analog com Example LDF file for VisualDSP Example EE 62 Page 4 Notes on using Analog Devices DSP components and development tools Phone 800 ANALOG D FAX 781 461 3010 EMAIL dsp support analog com FIP ftp analog com seg_init INPUT_SECTIONS OBJECTS seg_init LIBRARIES seg_init gt seg_init seg_pmco INPUT_SECTIONS OBJECTS seg_pmco LIBRARIES seg_pmco gt seg_pmco alt_pmco INPUT_SECTIONS OBJECTS seg_pmco gt alt_pmco seg_dmda INPUT_SECTIONS OBJECTS seg_dmda LIBRARIES seg_dmda gt seg_dmda INPUT_SECTIONS OBJECTS alt_dmda gt alt_dmda stackseg allocate a stack for the appl
4. h we used for the VisualDSP development tools example is not available for the v3 3 tools To accommodate this we therefore need to do things in a more tedious manner There is one main difference to our approach here we must compile the source file separately to place it in the desired segment by using the mpmdata compiler switch For more information on this compiler switch please refer to sections 3 2 5 and 3 2 6 on pages 3 8 and 3 9 of the ADSP 21000 Family C Tools Manual third edition g21k short 33 c c mpmdata alt_dmda a 21060c ach save temps g For the above example we see that we have compiled our source file named short 33 c which will reside in the segment named alt_dmda which we have declared in our architecture file Here is an excerpt of this file below SEGMENT RAM BEGIN 0x0007c000 END 0x0007ffff DM WIDTH 16 alt_dmda For our configuration our short word memory space begins at 2 0x3E000 and ends at 2 0x3FFFF or 0x7C000 to Ox7FFFF Also note the inclusion of the c compiler switch This switch stops the compiler from invoking the linker so only an object file is created not an executable This important step is needed because we need to compile our different segment s sources separately and then link them all together to create the final executable A complete example will be provided in the appendix at the rear of this EE note Manipulating Signed 16 bit Data If our 16 bit da
5. ication ldf_stack_space ldf_stack_length MEMORY_SIZEOF seg_stak gt seg_stak heap allocate a heap for the application ldf_heap_space ldf_heap_end Idf_heap_space MEMORY_SIZEOF seg_heap 1 ldf_heap_length ldf_heap_end Idf_heap_space gt seg_heap Example LDF file for VisualDSP example ontinued EE 62 Page 5 Notes on using Analog Devices DSP components and development tools Phone 800 ANALOG D FAX 781 461 3010 EMAIL dsp support analog com FIP ftp analog com Short Word memory space in C example for VisualDSP development tools static segment alt_dmda int x static segment alt_dmda int shortArray 10 1 2 3 4 5 6 7 8 9 10 static segment alt_dmda int total void main void for i 0 i lt 10 i total shortArray 1 total x asm idle l and af main Example source code for VisualDSP short word memory example EE 62 Page 6 Notes on using Analog Devices DSP components and development tools Phone 800 ANALOG D FAX 781 461 3010 EMAIL dsp support analog com FIP ftp analog com Appendix B v3 3 Development Tools Example SYSTEM Example_ADSP21060_C_Architecture PROCESSOR ADSP21060 SEGMENT RAM BEGIN 0x00020000 END 0x000200ff PM WIDTH 48 seg_rth SEGMENT RAM BEGIN 0x00020100 END 0x000217ff PM WIDTH 48 seg_init SEGMENT RAM BEGIN 0x00021800 END 0x00025fff PM WIDTH 48 seg_pmco SEGMENT RAM BEG
6. lt_dmda int The above statement will tell the compiler and linker to place the array labeled shortArray into the memory segment alt_dmda which is declared in your LDF file Setting Up Your LDF Setting up alternate segments in your LDF file is a very straightforward procedure Here is an excerpt from the LDF used for this EE note a complete version of this file and all of the sources used for the project are included in the appendix at the rear of this document MEMORY alt_dmda TYPE DM RAM START 0x0007c000 END 0x0007ffff WIDTH 16 PROCESSOR p0 LINK_AGAINST COMMAND_LINE_LINK_AGAINST OUTPUT COMMAND_LINE_OUTPUT_FILE SECTIONS alt_dmda INPUT_SECTIONS OBJECTS alt_dmda gt alt_dmda From this LDF example we see that our segment is declared in a short word segment in the memory field of command specifies the physical memory of the target system with the sections portion of the LDF corresponding to each memory segment declared For more information on these linker description file commands please refer to pages 5 33 ANALOG DEVICES through 5 35 of the VisualDSP User s Guide amp Reference Manual first edition V3 3 210xx Family Development Tools Example For the v3 3 version of our development tools the placement of variables into alternate memory segments is performed in a different manner Unfortunately for us the static segment qualifier whic
7. ord memory space in C example for v3 3 development tools extern int x extern int shortArray extern int total void main void int i for i 0 i lt 10 i total shortArray i total x asm idle end of main Main source file Main c for v3 3 development tools Short 33 c Short Word memory space in C example for v3 3 development tools int x int shortArray 10 1 2 3 4 5 6 7 8 9 10 int total Short word memory segment file Short 33 c for v3 3 development tools EE 62 Page 8 Notes on using Analog Devices DSP components and development tools Phone 800 ANALOG D FAX 781 461 3010 EMAIL dsp support analog com FIP ftp analog com
8. sed to access 16 bit data located in the internal memory of the SHARC The short word address space is an alias of the normal word address space Each single 32 bit memory address in normal word space becomes two 16 bit words in short word address space See page 5 12 of the SHARC User s Manual for the respective memory map Each memory address in Normal word memory space can be accessed as two short words by doubling the address For example say we had a value of 0x12345678 stored at memory address 0x28000 This is the first location of memory block on a 21062 A read memory location 0x56000 would return the LSW of the value stored at 0x28000 0x5678 and an access to location 0x56001 would return the MSW of the value stored at 0x28000 0x1234 For more information on this concept read sections 5 2 and 5 3 4 of the SHARC User s Manual The C compiler does not directly support short word memory space so we need to take care of a few things manually Fortunately for us the development tools for the SHARC family compiler allow us to place variables and other datatypes into whichever memory segment you choose VisualDSP Development Tools Example The VisualDSP development tools allow you to easily place variables into an explicit memory segment that you declare in your linker description file LDF using the segment qualifier For example in your C source you would include the following statement Static segment a
9. ta is signed data we can use the Short Sign Extend mode of the SHARC which will sign extend our 16 bit values when they are loaded into 32 bit 40 bit the register file asm bit set MODE SSE EE 62 One important statement to mention here is that the SHARC family DSP processors work natively with 32 bit datatypes When using short word memory accesses you must ensure that you deal with your signed data values accordingly Writes from the register file to 16 bit memory work as desired whether the data is a negative or a positive value Reading a negative value from memory into the register file should be sign extended to retain the sign information otherwise undesired calculations and values will result Page 2 Notes on using Analog Devices DSP components and development tools Phone 800 ANALOG D FAX 781 461 3010 EMAIL dsp support analog com FTP ftp analog com Appendix A VisualDSP Example Link for 21060 system ARCHITECTURE ADSP 21060 SEARCH_DIR ADI_DSP 21k lib MAP SUM map The 1ib060 dlb must come before libc dlb because libc dlb has some 21020 specific code and data LIBRARIES lib060 dlb libc dlb Libraries from the command line are included in COMMAND_LINE_OBJECTS OBJECTS 060_hdr doj COMMAND_LINE_OBJECTS MEMORY seg_rth TYPE PM RAM START 0x00020000 END 0x000200ff WIDTH 48 seg_init TYPE PM RAM START 0x00020100 END 0x000217ff WIDTH 48 seg_pmco TYPE P
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