feat(boot): new stack initialization routine

code/boot/src/reset.s

@@ -16,8 +16,21 @@
   EXPORT RESET
 
 RESET
+
+CLRSTACK
+  ; Initialize the system stack
+  lda #$00           ; Initialize A & X to zero out the stack
+  ldx #$0000
+NEXT@
+  sta STACK_BOTTOM,x ; Write a zero and progress to the next byte
+  leax 1,x
+  cmpx #STACK_DEPTH  ; See if we're at the top of the stack yet
+  blo NEXT@          ; Loop if we aren't at the end yet
+  lds STACK_TOP      ; Set S to top of newly cleared stack
+
+SERINIT
   ; 8n1 Serial Enable DLAB
-  lda #UARTF_LCR_WLS | UARTF_LCR_DLAB
+  lda #UARTF_LCR_WLS|UARTF_LCR_DLAB
   sta UART_LCR
   ; REVIEW: Potential endianness hiccough here
   ldd #$0C00           ; Set divisor to 12 (9600 baud)
@@ -29,7 +42,8 @@ RESET
   sta UART_MCR
   lda #'H               ; send 'H'
   sta UART_BUFR
-WAIT@
+
+WAIT
   sync                 ; Wait for interrupts
   nop
-  bra WAIT@
+  bra WAIT