merged

main.S

@@ -7,6 +7,29 @@
 #define SP r1
 #define SR r2
 
+;; --- register usage --------------------------------
+;; r4: synchronization between main loop and isr
+;;     bit0 signals byte done from isr
+;; r5: data byte to be handled by isr
+;; r6: bit-counter, only used within isr
+;; r7: screen data start/next pointer
+;; r8: screen data end pointer
+;; r9: next screen data byte, prepared in mainloop
+
+#define SIGNAL_INIT_VALUE 0x00
+#define SIGNAL_BYTE_DONE 0x01
+#define SIGNAL_ISR_ENABLE 0x02
+#define SIGNAL_REGISTER r4
+
+#define DATA_BYTE_REGISTER r5
+#define NEXT_DATA_BYTE_REGISTER r9
+#define DATA_NEXT_ADDRESS_REGISTER r7
+#define DATA_LAST_ADDRESS_REGISTER r8
+
+#define BIT_COUNTER_REGISTER r6
+#define BIT_COUNTER_INIT_VALUE 0x01
+;; ---------------------------------------------------
+
 
   .section ".rodata","a"
 screendata:
@@ -43,20 +66,17 @@ green:
   .section ".text","ax",@progbits
 _start:
   ;; disable watchdog
-  mov.w   #WDTPW|WDTHOLD,&WDTCTL
+  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
+  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
 
-  mov.w   #0xaaaa, r7
-  mov.w   #0x5555, r8
-
 init:
   ;; configuration of GPIO Ports
   mov.b   #BIT0|BIT1|BIT2,&P1DIR
@@ -67,16 +87,16 @@ init:
   ;; timer configuration
   ;;  configure and stop timer
   ;;  cycle time is 56.25ns
-  mov.w   #ID_0|MC_0|TACLR|TASSEL_2,&TA1CTL
+  mov.w   #ID_0|MC_0|TACLR|TASSEL_2, &TA1CTL
   ;;  2.0us 
-  mov.w   #45,&TA1CCR0
+  mov.w   #45, &TA1CCR0
   ;;  a bit less
-  mov.w   #10,&TA1CCR1
-  mov.w   #22,&TA1CCR2
+  mov.w   #10, &TA1CCR1
+  mov.w   #22, &TA1CCR2
   ;;  configure output mode for TA0.1
-  mov.w   #CCIE,&TA1CCTL0
-  mov.w   #OUTMOD_7,&TA1CCTL1
-  mov.w   #OUTMOD_7,&TA1CCTL2
+  mov.w   #CCIE, &TA1CCTL0
+  mov.w   #OUTMOD_7, &TA1CCTL1
+  mov.w   #OUTMOD_7, &TA1CCTL2
 
   ;; initialize bit-counter for isr
   mov.b   #0x01,r6
@@ -89,15 +109,11 @@ init:
   mov.w   #screendataend, r8
 
   ;; start timer in up mode
-  bis.w   #MC0,&TA1CTL
+  bis.w   #MC0, &TA1CTL
   ;; enable interrupts
   eint
 
 
-
-
-  ;; r4: synchronization between mainloop and isr
-  ;; r5: data byte to be handled by isr
 mainloop:
   ;; prepare next byte to handle by isr
   cmp.w   r7,r8
@@ -108,8 +124,9 @@ mainloop:
   inc.w   r7
 
 mainloop_wait_for_isr:
-  ;; check bit0 in sync register
-  bit     #0x01,r4
+  ;; check bit0 in sync register, wait for the signal from 
+  ;; the isr
+  bit     #SIGNAL_BYTE_DONE, SIGNAL_REGISTER
   jz      mainloop_wait_for_isr
 
   ;; load data
@@ -130,8 +147,6 @@ mainloop_data_done:
   jmp     mainloop
 
 
-
-
 ; --- timer isr ---
   ;; r6: exclusively used by isr as bit-counter
 timer1_a0_isr:
@@ -156,7 +171,7 @@ timer1_a0_isr_end:
   jnc     timer1_a0_isr_exit
 
   ;; reset bit-counter
-  mov.b   #0x01,r6
+  mov.b   #BIT_COUNTER_INIT_VALUE, BIT_COUNTER_REGISTER
   ;; signal byte done
   bis     #0x01,r4
 
@@ -171,13 +186,6 @@ timer1_a0_isr_exit:
   reti
 
 
-
-;timer0_a1_isr:
-;  reti
-
-; --- interrupt vectors ---
-;  .section "__interrupt_vector_9","ax",@progbits
-;  .word   timer0_a1_isr
   .section "__interrupt_vector_14","ax",@progbits
   .word   timer1_a0_isr