1. Assembly and Linear Assembly Evgeny Kirshin, 05/10/2011
ECSE436 Tutorial
Assembly and Linear Assembly
Evgeny Kirshin,
05/10/2011

2. Outline Introduction to Assembly Linear Assembly AMR Reading
Demo: simple sine-wave generator

3. TMS320 Assemby Language

4. C6000 ISA

5. Instruction Packing

6. Sample Instructions

7. Sample Instruction

8. Instruction List

9. Instruction List

10. C program calling and ASM function

11. C program calling and ASM function
-Values passed to the assembly functions using registers : A4,B4,A6,B6 and so on
-Only registers A1,A2,B0,B1,B2 can be used as conditional registers
-B3 contain the return address
-A4 is the return value
-Need to take into account the NOP

12. Linear Assembly
To effectively program a DSP using assembly language, you need to do the scheduling by hand!
Need to account for the number of clock cycles each functional unit takes, etc…
Difficult, so TI has linear assembly
you don’t have to schedule it, the compiler does it for you
can use CPU resources without worrying about scheduling, register allocation, etc…

13. C code TI Linear Assembly Assembly What is Linear Assembly ?
Efficiency
Ease of use
Assembly

14. What is Linear Assembly ?
It is a cross between C and Assembly
Enables you to write assembly-like programs
It lets you :
use symbolic names
forget pipeline issues
ignore putting NOPs, parallel bars, functional units, register names
more efficiently use CPU resources than C (e.g., hardware circular buffers)

15. File extensions File extension for c is .c
File extension for linear assembly is .sa
File extension for low-level assembly is .asm

16. Example Dot Product //DOTPclasm.c
From Chassaing
//DOTPclasm.c
short dotp4clasmfunc(short *a, short *b, short ncount);
#include <stdio.h>
#define count 4
short x[count] = {0,1,2,3};
short y[count] = {100, -20, 30, -20};
volatile int result = 0;
main() {
result = dotp4clasmfunc(x,y,count);
printf("result = %d decimal \n", result); }
Function written in LASM

17. Example Dot Product The LASM code .def _dotp4clasmfunc
From Chassaing
The LASM code
.def _dotp4clasmfunc
_dotp4clasmfunc: .cproc ap, bp, count
.reg a, b, prod, sum
zero sum
loop: ldh *ap++,a
ldh *bp++,b
mpy a,b,prod
add prod,sum,sum
sub count,1,count
[count] b loop
.return sum
.endproc

18. Example Dot Product Define and ASM function called from C
From Chassaing
Define and ASM function called from C
.def _dotp4clasmfunc
Name of the function
Start a section of Linear assembly
_dotp4clasmfunc: .cproc ap, bp, count
Arguments of the function
Set up your variables (similar to C)
.reg a, b, prod, sum

19. Example Dot Product Initialize your sum to zero
From Chassaing
Initialize your sum to zero
zero sum
Load the value from memory pointed by ap,
copy it to register a and increment the pointer by 1
ldh *ap++,a
ldh stands for load half word (a short in C)
Do the same thing with b
ldh *bp++,b

20. Example Dot Product Multiply a and b and write the result to prod
From Chassaing
Multiply a and b and write the result to prod
mpy a,b,prod
Add sum and prod and write the result to sum
add prod,sum,sum
Decrement count by 1
sub count,1,count

21. Example Dot Product If count is different than 0, branch to loop
From Chassaing
If count is different than 0, branch to loop
[count] b loop
Return sum as the output of your function (exactly
Like the return command in C)
.return sum
End linear assembly function
.endproc

22. Circular Addressing

23. Addressing mode register
AMR
Addressing mode register
Read Chassaing at pages : 82-83

24. Addressing mode register
AMR
Addressing mode register

25. Addressing mode register
AMR
Addressing mode register
How to modify the AMR ?
MVKL .S2 0x0004,B2
MVKH .S2 0x0005,B2
MVC .S2 B2,AMR
MVC is the only function which can modify the
content of a control register
Be sure to reset the AMR at the end of your function
Also, do the same inside your interrupt routine, check the book
by Chassaing to know how to modify the AMR from C
There is a good description on how AMR works in SPRA645, see further

26. References: TI documents
TMS320C6000 Optimizing Compiler User's Guide (SPRU187).
Chapter 4 contains the description of the directives (.trip, .cprog, .reg, etc.)
TMS320C67x/C67x+ DSP CPU and Instruction Set Reference Guide (SPRU733).
Contains the description of the instruction set (add, mpy, sub, mv, etc.)
TMS320C6000 Assembly Language Tools (SPRU186V).
Circular Buffering on TMS320C6000 (SPRA645).
Nice description of hardware circular buffering and the AMR register

27. References: books Chaissaing, pages : 87-88 and 112-115
Kuo and Gan, pages :
Additional book:
S.A.Tretter. Communication System Design Using DSP Algorithms. SpringerLink, 2008
Contains good description of the AIC, McBSP, interrupts and sine-wave generation examples. Available online in PDF (from McGill).

28. Questions ?