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ANALOG DEVICES Using Code Overlays from ROM on the ADSP-21161N EZ-KIT Lite Manual

1. loop to determine how many total sections there are in the overlays prior to overlay 3 Then we place that result in an arbitrary register R8 We have an index register I9 pointing to the beginning of the total live_addr buffer After we determine the number of sections there are prior to overlay 3 we place that value in modifier M11 Then update the index register I9 with the modify value We now have I9 pointing to the information location for overlay 3 In the case where we are DMAing overlay 1 we do not need to calculate the modify value because we know that its information is located at the beginning of the buffer Check Number of Sections The next objective is to check the number of sections in the overlay to be DMAed In order to setup the DMA properly we need to know the e live address of the code location in PROM to DMA from e run address of code location in internal memory to DMA to e number of internal words to transfer size that code will take up in internal memory and e number of external words to transfer size of code in PROM to read from Listing 3 Plit as defined in the Idf file PLIT RO PLIT_SYMBOL_OVERLAYID R1 PLIT_SYMBOL_ADDRESS JUMP _OverlayManager For single section overlays these parameters are simple to determine The run address is provided Page 5 of 9 when the overlay is first called For this application it is stored in R1 See Listing 3 For more informati
2. overlay 1 0x4020B 00 00 00 00 00 00 0x4021D nops end section 2 overlay 1 Using Code Overlays from ROM on the ADSP 21161N EZ KIT Lite EE 180 ANALOG DEVICES 0x4021E 06 BE 00 04 02 3A 0x4021F 0x40221 End of section 3 overlay 1 0x40222 nops begin section 4 overlay 1 0x40223 00 00 00 00 00 00 0x40235 nops end section 4 overlay 1 0x40236 06 BE 00 04 02 3A 0x40237 0x40238 End of section 5 overlay 1 Figure 5 space 0x4200DEC 0x4200DED 0x4200DEE 0x4200DEF 0x4200DF0 0x4200DF1 0x4200E21 0x4200E22 0x4200E2D 0x4200E3A 0x4200E3B 0x4200E3C 0x4200E3D Illustration of overlay live End of section 1 Section 2 Tag Count Address Info 3A 02 04 00 Page 6 of 9 0x4200E3E BE 0x4200E3F 06 0x4200ES1 End of section 3 0x4200E52 Section 4 Tag 0x4200E5D Count Address Info Ox4200E6A 3A 0x4200E6B 02 0x4200E6C 04 0x4200E6D 00 0x4200E6E BE 0x4200E6F 06 0x4200E99 End of section 5 Now let s examine the procedure to bring a multiple section overlay such as the one shown in Figures 4 and 5 into internal memory By checking the section type info in the total sec_type buffer we know that section 1 of overlay 1 contains code Therefore we need to determine the live address of th
3. the section size in the PROM we multiply the internal word size by 6 Adding this to the beginning address of the code we get the next section s starting location in the PROM Example 1 Locating the next section s address from a code type Type 0x15 Code Code begins at 0x4200E3A Internal size of code OxA Page 2 of 9 0x4200E3A 0x4 6 0x4200E52 To accurately locate the address of the next section s info the section type must be correctly interpreted For the example shown in Figure 1 the section tag beginning at address 0x4200E52 is 0x19 and the count is 0x14 This tag indicates a zero type and the count indicates an internal word size of 0x14 This is an equivalent of 0x78 8 bit locations in the PROM However for zero types the loader does not generate all the zeros and fill up the PROM with zeros This would be a waste of valuable space Instead only the tag count and live address are provided Later in the discussion of the overlay manager we will discuss how to handle the zero type sections For the purpose of the check_routine now we only need to know that for zero type sections we find the next section s address by simply adding 0xC to the current PROM address to account for the space that the tag count and address info takes up in the PROM Example 2 Locating the next section s address from a zero type Type 0x19 Zero Section info begins at 0x4200E52 0x4200E52 OxC 0x4
4. 200ESE The Ovl Init asm file checks every sections info until it reaches a tag of 0x0 which indicates that there are no more sections Parsing Overlay Information Now that all the overlay sections information have been collected the Ovl_Sec_Info asm file parses it to determine e the number of section types in each overlay Using Code Overlays from ROM on the ADSP 21161N EZ KIT Lite EE 180 ANALOG DEVICES e account for the overlay id information that s embedded in the loader file To check how many sections are in each overlay we compare the individual section sizes to the entire overlay size In the check routine of the previous file we placed all the section sizes into the total _sec_size buffer At run time the linker also generates constants with each overlay s total run size Therefore by comparing the individual section size to the entire overlay size we can find out how many sections are in each overlay This information is stored in the num ovl _sec buffer When the loader file is created the overlay id is embedded after the tag count and address info For overlays with multiple sections the overlay id is embedded only once after the overlay s first set of tag count and address info Figure 2 illustrates this Figure 2 Illustration of overlay id embedded in section info in PROM Ovl 1 Sec 1 0x4200DDA Tag Count Address 0x4200DE6 Overlay ID 1 0x4200DEC Cod
5. Engineer To Engineer Note EE 180 ANALOG Technical Notes on using Analog Devices DSP components and development tools Contact our technical support by phone 800 ANALOG D or e mail dsp support analog com DEVICES Or visit our on line resources http www analog com dsp and http www analog com dsp EZAnswers Using Code Overlays from ROM on the ADSP 21161N EZ KIT Lite Contributed by C Lam Introduction Software overlays are very useful in systems that have tight memory constraints In the case where internal memory is limited and adding external RAM significantly increases cost importing overlays from the boot ROM provides a feasible and relatively simple solution One of the main obstacles in accomplishing this is to determine the residing location of the overlay s in the ROM Currently the VisualDSP 2 0 linker does not provide this support Therefore the first of the three main parts of this application runs through the boot image in the ROM to decipher which sections of code are part of an overlay After all the overlay sections are located the second main routine parses all the information collected by previously Finally the third main routine the overlay manager is responsible for importing the correct overlay when called Locating Overlay Information The code that locates the overlay information is implemented in the file Ovl_Init asm Its objective is to run through the PROM to check December 5 2002 whet
6. e Ovl 1 Sec 2 0x4200E22 Tag 0x4200E2E Ovl 2 Sec 1 Count Address Overlay ID 2 Page 3 of 9 It is important to account for the embedded overlay id information in order for the overlay manager to DMA the proper code section into internal memory The next two examples illustrate the correct calculation of the code s starting address in the PROM If section is the first of a multiple section overlay or a single section overlay use the following formula Start addr of section OxC 0x6 If section is part of a multiple section overlay but not the first section then there will be no overlay id embedded The code s starting address will immediately follow the tag count live address info Calculate according to the formula Start addr of section OxC Example 3 Locating the code s starting address with embedded overlay id Using Figure 2 Overlay 1 Section 1 Start addr of section info 0x4200DDA Locations for tag count address OxC Locations in PROM for overlay id 0x6 0x4200DDA 0xC 0x6 0x4200DEC Example 4 Locating the code s starting address without embedded overlay id Using Figure 2 Overlay 1 Section 2 Start addr of section info 0x4200E22 Locations for tag count address OxC 0x4200DDA 0xC 0x4200E2E The corrected section code start addresses are then written into the total_live_addr buffer Using Code Overlays fro
7. e code run address internal word size and external word size We know the live address by checking the total live addr buffer Because this is the first section of the overlay we know the run address is the run starting address for overlay 1 This is stored in R1 as shown in Listing 3 We know the internal word size by checking the total sec_size buffer And finally we know that for code the external word size is 6x the internal word size six 8 bit external words one 48 bit internal word The first section is now ready to be DMAed into internal memory Listing 4 shows the code sequence for the DMA process Using Code Overlays from ROM on the ADSP 21161N EZ KIT Lite EE 180 ANALOG DEVICES Listing 4 Code implementation of DMA routine for code sections Initially disable and clear out DMA channel 10 R12 0 DM DMAC10 R12 Write Live Address to EPBO external index address register previously read into R7 DM EIEPO R7 Setup EPBO external and internal index modify registers to R12 1 DM EMEP0 R12 DM IMEP0 R12 Save old value of SYSCON R13 DM SYSCON R12 BSET R13 BY 1 DM SYSCON R12 Write Run Address to EPBO internal index address register previously read into R5 DM IEP0 R5 Set number of Run internal words to transfer previously read into R9 DM CEP0 R9 Set number of Live external words to transfer Multiply Run i
8. gins at 0x4200E6A Using Code Overlays from ROM on the ADSP 21161N EZ KIT Lite EE 180 ANALOG DEVICES Figure 1 above shows an example illustration of three sections info in the PROM For this example after the first time the check_routine is initiated we will know 4 pieces of information RO 0x15 Section Type R2 0xA Section size R3 0x60003C Section live address Current PROM address 0x4200E2E The current PROM address can be read from the External Memory DMA Index register EIEPO0 We see that the value in R3 corresponds to the dummy live address that we ve assigned to overlays therefore we know that this particular section belongs to an overlay By checking the type info in RO we know that this section contains code Therefore accounting for the space that the tag count and address info takes up in the PROM 0xC locations we know that code begins at 0x4200E3A 0x4200E2E OxC At this point we record the type RO in the total sec_type buffer size R2 in the total sec_size buffer and real live address 0x4200E3A into the total live addr buffer To read the next section s info the check_routine increments the EIEPO to 0x4200E52 It calculates this address by using this formula Addr of code size of code 6 Six 8 bit locations in the PROM make up one internal 48 bit instruction The size of the code read into R2 is the internal word size Therefore to find
9. her each section of code belong to an overlay Parsing of this collected information is handled in the next section There are two main routines in this file e Read boot info from PROM e Check the boot info that was read The read_boot_ info routine simply reads from the PROM and places three pieces of information into registers RO R2 and R3 The tag info is placed in RO and it identifies what type of data or code this section consists The internal count info placed in R2 holds the number of words this section takes up in internal memory R3 holds the destination address info This is the address at which the overlay has been defined to reside in also known as live address However since we are not having the overlays reside in internal memory the address generated by the linker and held in R3 will only be a dummy address Listing 1 Example memory definition of dummy address MEMORY memsdram TYPE PM RAM START 0x00600000 END 0x006FFFFF WIDTH 48 Copyright 2002 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 re
10. lay 1 we need to calculate the modifier value in order to access the start of the information for the overlay we are DMAing Page 4 of 9 Figure 3 illustrates the stored live addresses of four overlays with multiple and single section in memory Listing 2 provides the actual code to determine the modifier value for locating the starting information of overlay 3 Figure 3 Illustration of overlay section information in data buffer total_live_addr buffer 0x5030D Ovl 1 Sec 1 Live Addr in PROM 0x5030E Ovl 1 Sec 2 Live Addr in PROM 0x5030F Ovl 1 Sec 3 Live Addr in PROM 0x50310 Ovl 1 Sec 4 Live Addr in PROM 0x50311 Ovi 1 Sec 5 Live Addr in PROM 0x50312 Ov1 2 Sec 1 Live Addr in PROM 0x50313 Ov1 3 Sec 1 Live Addr in PROM 0x50314 Ov14 Sec 1 Live Addr in PROM 0x50315 OvI 5 Sec 1 Live Addr in PROM Listing 2 Code implementation for determining modifier value to locate starting information for overlay 3 Summation loop to determine total number of sections prior to overlay 3 Store sum in register R8 19 total_live_ addr 19 0x5030D M11 6 19 0x50313 M11 R8 modify 19 M11 In the Ovl Sec_Info asm file we ve determined the number of sections in each overlay To locate where the information for overlay 3 starts we Using Code Overlays from ROM on the ADSP 21161N EZ KIT Lite EE 180 ANALOG DEVICES implement a summation
11. liable however no responsibility is assumed by Analog Devices regarding the technical accuracy and topicality of the content provided in all Analog Devices Engineer to Engineer Notes In the example shown in Listing 1 above the linker would generate an address in the range of 0x600000 to Ox6FFFFF for overlays defined in the memsdram section Knowing that all of our overlays are placed in this dummy location in the range of 0x600000 to Ox6FFFFF we can check R3 each time after we read the boot info for a value within this range When we find a section with a destination address in this range we then know that it belongs to an overlay This is done in the check_routine portion of the Ovl_Init asm file Whenever an overlay section is discovered three pieces of information are written into designated buffers e the real live address that the overlay resides in ROM e the section count size from R2 and the section data or code type from RO In addition to determining whether a section belongs in an overlay the check_routine code also has to know how much to increment by to read the next section s information Figure 1 Illustration of info in PROM 0x4200E2E Tag Ox 5 Count 0x4 Address 0x60003C 0x4200E3A Code begins at 0x4200E3A 0x4200E52 Tag 0x19 Count 0x14 Address 0x600044 0x4200ESE Tag 0x15 Count 0x8 Address 0x60006C 0x4200E6A Code be
12. m ROM on the ADSP 21161N EZ KIT Lite EE 180 ANALOG DEVICES Overlay Manager The overlay manager handles the process of DMAing the code sections into internal memory zero filling instruction memory for zero type sections and executing the overlay When an overlay is called the overlay id and the run starting address are stored in registers RO and R1 respectively The overlay manager first checks whether the overlay called has been previously DMAed into internal memory already If so there is no need to DMA the overlay again The program simply jumps to the run starting address of the overlay and executes If the overlay is not in internal memory yet the process of setting up the DMA starts In order to setup the DMA properly we need to perform the following 1 Check whether the overlay to be DMAed is overlay 1 2 Check how many sections are in the overlay to be DMAed 3 Check section type to determine what DMA parameters are needed Check for Overlay 1 The section information for overlay 1 is always located at the beginning of the information buffers For example the first entry in the total live addr buffer would contain the live address of the first section in overlay 1 If the overlay to be DMAed is overlay 1 then we know that the modifier to our information buffers is 0 because the information to overlay 1 starts at the beginning of the buffer However if we checked that the overlay to be DMAed is not over
13. nternal words by 6 because six 8 bit external words one 48 bit internal word R9 R9 R15 uui DM ECEP0 R9 R12 0x421 DM DMAC10 R12 IDLE DM SYSCON R13 Enable DMA Restore SYSCON Page 7 of 9 After the first section has been DMAed into internal memory we begin to bring section two into internal memory By checking the next entry in the total_sec_type buffer for the next section s type info we realize that the section is a zero type For zero type sections no DMA is required The only pieces of information needed are the run address and number of internal words to transfer By reading the next entry in the total sec_size buffer we know the number of internal words to transfer To find the run address we implement a get_index routine in this application that keeps track of the run address where the last section ended As Figure 4 above shows the first section ends at address 0x40209 and the second section begins at address 0x4020A Listing 5 shows the code sequence for zero filling internal memory Listing 5 Code implementation of zero fill loop for zero type sections R5 contains the run address for the next section Load run address to I5 pointer 15 R5 PX contains 0x0 to zero fill memory PX 0x0 R9 contains the number of times to loop this section s internal size M5 contains 0x1 increment one after each write Icntt R9 do zero loop until lce zero_lo
14. on on plit tables and how overlays work in general see EE 66 By calculating the modifier value as shown in the previous section above the live address and number of internal words can be determined from the total live addr and total sec_size buffers respectively For the example shown in Figure 3 the single section overlays are overlay 2 3 4 and 5 Therefore after calculating the respective modifier values for each overlay we know that the live addresses for overlay 2 3 4 and 5 are 0x50312 0x50313 0x50314 and 0x50315 respectively After the internal word size is determined from the total _sec_size buffer the external size is just 6x the internal size six 8 bit external words one 48 bit internal word For multiple section overlays the DMA parameters are more difficult to determine The reason is because each section needs to be DMAed separately and the run address of where the last section ended must be kept track of constantly Also the code has to check whether the section is a zero type If so no DMA is performed Instead a zero loop will fill instruction memory with zeros for the count size of the section Figures 4 and 5 illustrate how the overlay maps from external PROM memory space to internal instruction memory space Figure 4 Illustration of overlay run space 0x40201 OF 71 00 00 00 00 0x40202 J anana 0x40209 End of section 1 overlay 1 0x4020A nops begin section 2
15. op DM I5 M5 PX Depending on whether the section is a code or zero type the application continues the DMA or zero fill implementation in Listings 4 and 5 until it detects that all the sections in this overlay have been brought into internal memory At that point it jumps to the run starting address of the overlay stored in R1 see Listing 3 and begins execution of the code Using Code Overlays from ROM on the ADSP 21161N EZ KIT Lite EE 180 ANALOG DEVICES Page 8 of 9 ANALOG DEVICES References EE 66 Using Memory Overlays EE 151 Implementing Software Data Overlays for the ADSP 21161 Using the EZ KIT Linker and Utilities Manual for ADSP 21xxx Family DSP s ADSP 21161 SHARC DSP Hardware Reference Manual Document History Version Description December 5 2002 by C Lam Initial Release Using Code Overlays from ROM on the ADSP 21161N EZ KIT Lite EE 180 Page 9 of 9

ANALOG DEVICES Using Code Overlays from ROM on the ADSP-21161N EZ-KIT Lite Manual

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