Engineer To Engineer Note EE-42
Contents
1. define SYSCON int Ox000 Using this pointer assignment it is now possible to change the content of the System Control register in the C file with the following instruction SYSCON 0x1234 Attached to this note is a header file def06xc h that already defines some IOP registers This file has to be included at the beginning of your program to grant this comfortable way of accessing IOP control registers The syntax is include lt def06xc h gt 6 Embedded Assembly Language 6 1 Accessing Core Processor System Registers The core processor system registers MODE1 MODE2 ASTAT STKY IRPTL IMASK IMASKP USTATI amp Page 2 Notes on using Analog Devices DSP audio amp video components from the Computer Products Division Phone 800 ANALOG D or 781 461 3881 FAX 781 461 3010 EMAIL dsp support analog com USTAT2 are not memory mapped and due to this they could not be accessed via the above mentioned syntax These registers could only be modified by using the inline assembler feature asm lst instruction 2nd instruction last instruction To be able to manipulate the bits of these core processor system registers in an easy way include the def21060 h header file at the beginning of your inline assembler code e g asm include lt def21060 h gt bit set imask LP2I bit set model IRPTEN Any other assembler instruction could be placed within the asm directive 6 2 Inline2. Assembler Instructions The above mentioned syntax could be used to place any valid assembler instruction within in c source code This is sometimes very useful if you wish to have a minimum of overhead for example for time critical program parts 6 3 Calling Assembler Subroutines It is also possible to call assembler routines out of the c main program A detailed description could be found in the C TOOLS MANUAL chapter 4 If you want to call external assembler subroutines or functions from the main C code the easiest way to link these different programming languages is to invoke the g21k compiler in the following way g21k filel c file2 asm a 21062c ach o out exe In this way you do not have to care about how to invoke the linker 1d21K File main c calls external asm subroutine mul2 to multiply two numbers extern float mul2 float x float y main float a 0 25 float b 0 75 float c c mul2 a b call assembler subroutine idleQ EE 42 File extmul asm include lt asm_sprt h gt segment pm seg_pmco global _mul2 _mul2 leaf_entry f0 f4 f8 fetch first and second parameter leaf_exit endseg 7 Example 1 Interrupts in C The irql c is just a small demo program that illustrates how to program interrupts in C language The demo could be run on the ADDS 2106x EZ LAB and by pressing the interrupt button on the board the LED connected to flagO of the ADSP 2106x will to
3. Engineer To Engineer Note EE 42 Notes on using Analog Devices DSP audio amp video components from the Computer Products Division Phone 800 ANALOG D or 781 461 3881 FAX 781 461 3010 EMAIL dsp support analog com C Programs on the ADSP 2106x Last Modified 6 25 96 This application note gives a brief introduction in programming Analog Devices SHARC DSP in C language Attached to this note are two C examples files irql c and linkdma c A brief description of their purpose is given below All programs have been written with the development software ADDS 210XX SW PC release 3 3 and have been tested on the ADDS 2106x EZ LAB Note that there is a new C compiler on the FTP site ftp analog com Attached files 21062c ach 21060c ach def06xc h linkdma c irql c 1 Read The Release Note There are some restrictions regarding the software tools Please read the release notes to be firm with the restrictions of your development software 2 Writing An Architecture File The architecture file is used to describe your target system on which the C program should run There are two ACH files attached to this application note 21062C ACH could be used to run C code on the EZ LAB and the 21060c ACH is for people who upgraded their EZ LAB with an ADSP 21060 The CINIT CSTACK and CHEAP directives are only used for C programming and are described in the C TOOLS MANUAL on page 3 3 ff The attached ACH files are only exampl
4. ansmit data via DMA channel 5 from a source buffer to a destination buffer The loop back mode is enabled by assigning two different link buffers to the same link port In this case both link buffer 2 and 3 are assigned to link port 3 The double clock rate of the Analog Devices DSP is used to transmit this data For further details about link ports see in the SHARC user s manual PRG that generates some sample values stores them in buffer source and transmit them via LINKDMA to buffer dest Date include lt stddef h gt include lt ctype h gt include lt stdlib h gt include def06xc h header file of register definitions define N 16 void main void VAR source buffer for transfer destination buffer static dm float source N static dm float dest N int i MAIN for i 0 i lt N i source i float i create some values for the transfer II5 int amp source II4 int amp dest set DMA pointer to start of source buffer set DMA pointer to start of dest buffer IM5 1 IM4 1 C5 N C4 N set DMA modify source to 1 set DMA modify dest to 1 set DMA count to lenght of buffer set dma count to length of buffer LCOM 0x0c0 double clock rate for transmission LAR 0x03f03f LAR register set LBUF2 gt port0 LBUF3 gt port0 32 Bit data LBUF2 rx LBUF3 tx
5. enable DMA INLINE ASSEMBLER LCTL 0x0b300 asm include lt def21060 h gt bit set imask LP2I enable link buffer 2 interrupt EE 42 bit set model IRPTEN INLINE END global interrupt enable idle set ADSP 2106x in idle state PRG END Notes on using Analog Devices DSP audio amp video components from the Computer Products Division Phone 800 ANALOG D or 781 461 3881 FAX 781 461 3010 EMAIL dsp support analog com Page 4
6. es to allow a quick start and if you wish to divide up your memory in another way refer to the USER S MANUAL in chapter 5 3 Writing And Compiling C Code After you wrote your c code the compiler should be invoked in the following way g2I1k code c a 21062C ach o output g The g switch is used to generate debuggable code for the simulator and emulator If you want the compiler to produce an optimized code use one of the following switches O O2 03 But remember that it is not possible to use the CBUG feature for code that has been optimized Furthermore the iterators ITER of the numerical C extension does not work with the O3 switch Using any optimization switches often cause the following problem If a variable is checked in a loop but is not updated in that loop the compiler removes the test of this variable out of the loop to minimize the number of instructions This could cause problems when the value of this variable is updated within an interrupt service routine and should be evaluated in the main loop To avoid this behavior it is necessary to declare this variable as volatile e g volatile int test_flag Sometimes customers wish to place C Functions not in the default segment seg_pmco but in a different one This could be easily done with the G21K EXE compiler e g There is a main program sum c and an external function ext c both written in C language The main program calls the external function
7. ggle The code is well documented and for further information refer to the C TOOLS MANUAL program that demonstrates the function of the irq button on the ADDS 2106x EZ LAB The flagO is toggled when you push the irq button Date include def06xc h defines IOP registers to access them in c language include lt signal h gt include file for the interrupt stuff volatile int irq1_occured void irq _handler int signal irq routine that toggles flag on the lab irql_occured 1 set irql flag asm bit tgl astat 0x080000 toggle flag using inline assembler void main void INLINE ASSEMBLER asm include lt def21060 h gt configure flag direction bit set mode2 FLGOO bit clr mode2 FLG1O bit set mode2 FLG20 bit clr mode2 FLG30 nop END INLINE FLAGO output FLAGI input FLAG2 output FLAG3 input irq1_occured 0 interrupt SIG_IRQ1 irq1_handler irq handler routine while 1 idle if irq1_occured Page 3 Notes on using Analog Devices DSP audio amp video components from the Computer Products Division Phone 800 ANALOG D or 781 461 3881 FAX 781 461 3010 EMAIL dsp support analog com irq1_occured 0 8 Example 2 Linkport DMA in C The following code is referred to the assembler code in the SHARC user s manual page 9 29 and uses the link port loop back feature to tr
8. in the alternative code segment alt_pmco PRG that calls an external c function in an alternate code segment extern int sum int a int b void main void VAR i sum i j idleQ PRG END The external functions could look like the following code int sum int a int b return a b To compile this example use the command lines ANALOC DEVICE g21k sum c c a 21062c ach g21k ext c c mpmcode alt_pmco g21k sum o ext o a 21062c ach o sum map g The mpmcode switch chooses the alternative code segment Variables placed in the dm pm memory space could be placed in an alternative segment by invoking the compiler with a similar switch mdmdata pmdata 4 Extensions to ANSI C The Analog Devices C compiler is based on the GNU software and supports ANSI C Nevertheless there are some extensions which are very useful As it is possible to store data either in the program or data memory of the Analog Devices DSP an additional keyword indicates where variables are placed by the linker Use the PM directive to place variables in program memory and the DM directive to place them in data memory e g float dm source 16 float pm dest 16 When no directive is given the linker will place the variable in the data memory by default The default memory segment in which the dm variables are placed is labeled seg_dmda and the default segment for variables which reside in program memo
9. ry space is called seg_pmda Often itis useful to place the variables in different segments for example external memory space An easy way to do this is to use the delivered include file macros h To use this comfortable feature add the directive include lt macros h gt to your source code and use the following syntax DEF_VAR name type seg mem name variable name type the actual C type seg the segment in the architecture file mem the memory that the variable exists in pm dm Another useful macro is called DEF _PORT which has nearly the same syntax as the above mentioned one This EE 42 macro could be used to define an IO port in C language The syntax is DEF_PORT name type seg mem name variable name type the actual C type seg the segment in the architecture file mem the memory that the variable exists in pm dm The necessary segment declaration in the architecture file could look like the following line SEGMENT PORT BEGIN 0x00404000 END 0x00404000 DM Wwidth 32 mafeadrs It is worthy to have a look at the macros h file as there are a lot of useful declarations that are not documented yet Further extensions are described in the C TOOLS MANUAL chapter 5 5 Accessing IOP Registers Most of the SHARC s control registers are memory mapped to the address range from 0x0000 to 0x0100 To access these memory mapped IOP registers you could use the following syntax in your C code
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