Quiz 6.3: Difference between revisions

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Sections start their location counters at zero. The .bss directives don't advance the counter, because they go off to a different section. Assembly instructions take up bytes of memory according to what they are and their addressing mode. Whenever a .sect happens the location counter is reset to zero. I'm not certain about these, but here is what I came up with.
New sections start their location counters at zero. Assembly instructions take up bytes of memory according to what they are and their addressing mode. Whenever a .sect, or .text happens the location counter is reset to zero. There is more in section 2 of this [http://www.ti.com/lit/ug/slau131m/slau131m.pdf TI Manual on the Assembler]. This quiz is tailored to understanding the Assembly List file, that has a field for the location counter. Code Composer Studio doesn't generate this by default anymore. It is good to look at for this quiz though. I wasn't able to correctly get the location counter values correct without it, and I'm impressed if you got them. Fortunately we can still get it to make an assembly listing for us.


To get the Assembly List file, go into the Build Settings->Build->Advanced Options->Assembler, and tick the Generate listing file box.
*0x0000
[[File:assembly-listing-option.png|800px]]
*0x0000
Here is the listing file I got using the MSP430G2553 processor.
*0x0000
<nowiki>MSP430 Assembler Unix v15.12.3 Tue Nov 1 17:48:13 2016
*0x0002

*0x0008
Tools Copyright (c) 2003-2015 Texas Instruments Incorporated
*0x000a
../main.asm
*0x000c
PAGE 1
*0x000e

*0x000e
1 .cdecls C,"msp430.h" ; include c header
*0x0010
2 000000 .bss cnt,2 ; WDT second counter
*0x0002
3 000002 .bss cat,4
*0x0000
4 000000 .text ; program section
*0x0000
5 000000 4031 start: mov.w #0x0400,SP ; set stack pointer
000002 0400
6 000004 40B2 mov.w #0x5a18,&WDTCTL ; set WD timer interval
000006 5A18
000008 0000!
7 00000a 40B2 mov.w #0x00fa,&cnt ; 1 sec WD counter
00000c 00FA
00000e 0000!
8 000010 43D2 mov.b #0x01,&IE1 ; enable WDT interrupt
000012 0000!
9 000014 D3D2 bis.b #0x01,&P1DIR ; P1.0 output
000016 0000!
10 000018 D032 bis.w #0x0018,SR ; enable interrupts
00001a 0018
11 000006 .bss dog,2
12 00001c E3D2 wdt_isr: xor.b #0x01,&P1OUT ; toggle P1.0
00001e 0000!
13 000020 1300 reti ; return from interrupt
14 000000 .sect ".int10" ; WDT vector section
15 000000 0000! .word wdt_isr ; Watchdog ISR
16 000000 .sect ".reset" ; PUC vector section
17 000000 0000! .word start ; RESET ISR
18 .end

No Assembly Errors, No Assembly Warnings
</nowiki>

The second column of numbers is the location counter.

Latest revision as of 15:12, 2 November 2016

New sections start their location counters at zero. Assembly instructions take up bytes of memory according to what they are and their addressing mode. Whenever a .sect, or .text happens the location counter is reset to zero. There is more in section 2 of this TI Manual on the Assembler. This quiz is tailored to understanding the Assembly List file, that has a field for the location counter. Code Composer Studio doesn't generate this by default anymore. It is good to look at for this quiz though. I wasn't able to correctly get the location counter values correct without it, and I'm impressed if you got them. Fortunately we can still get it to make an assembly listing for us.

To get the Assembly List file, go into the Build Settings->Build->Advanced Options->Assembler, and tick the Generate listing file box. Assembly-listing-option.png Here is the listing file I got using the MSP430G2553 processor. 

MSP430 Assembler Unix v15.12.3 Tue Nov  1 17:48:13 2016

Tools Copyright (c) 2003-2015 Texas Instruments Incorporated
../main.asm                              
                            PAGE    1

       1                     .cdecls        C,"msp430.h"    ; include c header
       2 000000               .bss    cnt,2           ; WDT second counter
       3 000002               .bss    cat,4
       4 000000               .text                   ; program section
       5 000000 4031  start:  mov.w   #0x0400,SP      ; set stack pointer
         000002 0400 
       6 000004 40B2          mov.w   #0x5a18,&WDTCTL ; set WD timer interval
         000006 5A18 
         000008 0000!
       7 00000a 40B2          mov.w   #0x00fa,&cnt    ; 1 sec WD counter
         00000c 00FA 
         00000e 0000!
       8 000010 43D2          mov.b   #0x01,&IE1      ; enable WDT interrupt
         000012 0000!
       9 000014 D3D2          bis.b   #0x01,&P1DIR    ; P1.0 output
         000016 0000!
      10 000018 D032          bis.w   #0x0018,SR      ; enable interrupts
         00001a 0018 
      11 000006               .bss    dog,2
      12 00001c E3D2  wdt_isr:        xor.b   #0x01,&P1OUT    ; toggle P1.0
         00001e 0000!
      13 000020 1300          reti                    ; return from interrupt
      14 000000               .sect   ".int10"                ; WDT vector section
      15 000000 0000!         .word   wdt_isr         ; Watchdog ISR
      16 000000               .sect   ".reset"                ; PUC vector section
      17 000000 0000!         .word   start           ; RESET ISR
      18                    .end

No Assembly Errors, No Assembly Warnings

The second column of numbers is the location counter.

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