MSP430 cpu cycles

Are you joking?

R4, your loop index, is preloaded with 6 and then decremented, so you will get exactly 6 iterations of a loop containing 4 machine instruction, surely less than one hundred cycles (not millions). It seems your tool is completely broken.

Regards,

P.

Piergiuseppe Tundo said:

It seems your tool is completely broken.

And the long execution time is because the tool does single-stepping to determine the cycles.
If the code were free-running, with a port toggle at beginning and end and an external counter/timer attached, the execution time would be in the range of far below a millisecond.

Hello Anirudh,

I updated your code a little to demonstrate what the above posts explained (code below). I started Timer_A right before your code begins, so it will increment at every rising edge of the clock. Setting a breakpoint at “label” and running to this point will reveal how many clock cycles the program will take. You can see the value in Timer_A by using the memory browser at address 0x0170, or using the register view. After running your code Timer_A had the value 0x003D in it, so that’s 61 cycles. For more info on the timer please see the user guide (http://www.ti.com/lit/ug/slau144j/slau144j.pdf pg 355 I’m currently using the G2553).

Regarding CPU seconds, you are correct in your calculation: CPU seconds = CPU cycles/CPU CLK Frequency. So with 61 cycles, that’s about 61 us. Jen-Michael explained why this can be longer while using the debug tool.

 

Here’s the code:

;-------------------------------------------------------------------------------
; MSP430 Assembler Code Template for use with TI Code Composer Studio
;
;
;-------------------------------------------------------------------------------
            .cdecls C,LIST,"msp430.h"       ; Include device header file

;-------------------------------------------------------------------------------
            .text                           ; Assemble into program memory
            .retain                         ; Override ELF conditional linking
                                            ; and retain current section
            .retainrefs                     ; Additionally retain any sections
                                            ; that have references to current
                                            ; section
;-------------------------------------------------------------------------------
RESET       mov.w   #__STACK_END,SP         ; Initialize stackpointer
StopWDT     mov.w   #WDTPW|WDTHOLD,&WDTCTL  ; Stop watchdog timer

;-------------------------------------------------------------------------------
			mov.w	#0x0220,R7
			BIS		R7,TACTL				; initilize timer_A (using SMCLK & continuous)

			mov.w #06h,R4                                            ; Main loop here
			mov.w #arr1,R5
			mov.w #200h,R6

HERE		mov.w @R5+, 0(R6)

			incd.w 	R6
			dec		R4
			jnz		HERE

label		jmp label

arr1		.word 20,30,-1,2,50,4
;-------------------------------------------------------------------------------


;-------------------------------------------------------------------------------
;           Stack Pointer definition
;-------------------------------------------------------------------------------
            .global __STACK_END
            .sect 	.stack

;-------------------------------------------------------------------------------
;           Interrupt Vectors
;-------------------------------------------------------------------------------
            .sect   ".reset"                ; MSP430 RESET Vector
            .short  RESET

Let us know if you have any other questions!

-Nate

IAR have a nice simulation mode with trace, it shows that it take 74 cycles.