initial

main.S

@@ -0,0 +1,76 @@
+  .file "main.S"
+
+#include <msp430g2553.h>
+
+
+#define PC r0
+#define SP r1
+#define SR r2
+
+
+  ;; .text is the name of the section, it is a hint for the linker to
+  ;; allocate the section
+  ;; ax: a means allocatable by linker, x means executable
+  ;; @progbits is a hint for the linker to allocate this section into
+  ;; program memory (flash)
+  .section ".text","ax",@progbits
+
+_start:
+  ;; disable watchdog
+  mov.w   #WDTPW|WDTHOLD,&WDTCTL
+
+  ;; configure clock system to the highest frequency
+  mov.b   #DCO0|DCO1|DCO2,&DCOCTL
+  mov.b   #XT2OFF|RSEL0|RSEL1|RSEL2|RSEL3,&BCSCTL1
+  mov.b   #0,&BCSCTL2
+  mov.b   #0,&BCSCTL3
+
+  ;; initialize stack pointer with value from linker
+  mov.w   #__stack, SP
+
+init:
+  ;; configuration of GPIO Port1, use Bit6 as TA0.1
+  mov.b   #BIT6,&P1DIR
+  mov.b   #BIT6,&P1SEL
+
+  ;; timer configuration
+  ;;  configure and stop timer
+  ;;  cycle time is 56.25ns
+  mov.w   #ID_0|MC_0|TACLR|TASSEL_2,&TACTL
+  ;;  2.0us 
+  mov.w   #45,&TACCR0
+  ;;  a bit less
+  mov.w   #16,&TACCR1
+  ;;  configure output mode for TA0.1
+;  mov.w   #CCIE,&TACCTL0
+;  mov.w   #CCIE,&TACCTL1
+  mov.w   #OUTMOD_7,&TACCTL1
+  ;;  start timer in up mode
+  bis.w   #MC0,&TACTL
+
+  ;; enable interrupts
+  eint
+
+mainloop:
+  jmp     mainloop
+
+; --- timer isr ---
+;timer0_a0_isr:
+;  mov.b   #BIT0,&P1OUT
+;  reti
+
+;timer0_a1_isr:
+;  mov.b   #0,&P1OUT
+;  reti
+
+; --- interrupt vectors ---
+;  .section "__interrupt_vector_9","ax",@progbits
+;  .word   timer0_a1_isr
+;  .section "__interrupt_vector_10","ax",@progbits
+;  .word   timer0_a0_isr
+
+  ;; .resetvec comes from linker
+  .section ".resetvec","ax",@progbits
+  .word   _start
+
+  .end