Merge pull request 'serial' (#1) from serial into main

Reviewed-on: #1

code/boot/src/boot.s

@@ -10,6 +10,7 @@
 ;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+  SECTION "Reset"
   ORG ROM_BASE
 
 RESET
@@ -36,12 +37,44 @@ WAIT
   nop
   bra WAIT
 
+  SECTION "Serial"
+
+; Writes a char to the UART in non FIFO mode, preserves A.
+; @param b: char to write
+OUTCHAR
+  pshs a               ; Preserve A
+1
+  lda UART_LSR         ; if LSR.THRE == 1 then write
+  anda UARTF_LSR_THRE
+  bne 1B               ; Loop if UART not ready yet
+  stb UART_BUFR        ; Write char
+  puls a               ; Restore A
+  rts
+
+; Writes a null terminated string to the UART in non FIFO mode, clobbers A and
+; B.
+; @param x: null terminated string start address.
+OUTSTR
+  ldb x                ; Get the next value from X
+  cmpb #$00            ; Make sure that mother is non-null
+  beq 2F
+  leax 1,x             ; Increment X for our next char
+1                      ; Loop point for UART waiting
+  lda UART_LSR         ; Wait for UART to be ready
+  anda UARTF_LSR_THRE
+  bne 1B
+  stb UART_BUFR        ; Actually do our write
+  bra OUTSTR           ; Reset for the next char
+2                      ; Jump point for end of routine
+  rts
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;
 ;; Interrupt and Reset Vectors
 ;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
+  SECTION "Vectors"
   ORG VECS_BASE
 
 VECTORS