feat(boot): new baud setup routine

code/boot/src/reset.s

@@ -41,7 +41,7 @@ SERINIT
   lda #(UARTF_MCR_RTS) ; Enable Request-to-Send
   sta UART_MCR
   lda #'H               ; send 'H'
-  sta UART_BUFR
+  sta UART_THR
 
 WAIT
   sync                 ; Wait for interrupts

code/boot/src/serial.s

@@ -12,9 +12,25 @@
 
   SECTION SERIAL
 
+  EXPORT SETBAUD
   EXPORT OUTCHAR
   EXPORT OUTSTR
 
+; Initializes the UART.
+; @param d: new divisor
+SETBAUD
+  pshs a              ; Preserve A
+  lda UART_LCR        ; Set only the DLAB bit
+  ora #UARTF_LCR_DLAB
+  sta UART_LCR
+  puls a
+  sta UART_DLM        ; Store new divisor
+  stb UART_DLL
+  lda UART_LCR        ; Reset DLAB
+  anda #$FE
+  sta UART_LCR
+  rts
+
 ; Writes a char to the UART in non FIFO mode, preserves A.
 ; @param b: char to write
 OUTCHAR
@@ -23,7 +39,7 @@ NOTREADY@
   lda UART_LSR         ; if LSR.THRE == 1 then write
   anda UARTF_LSR_THRE
   bne NOTREADY@        ; Loop if UART not ready yet
-  stb UART_BUFR        ; Write char
+  stb UART_THR         ; Write char
   puls a               ; Restore A
   rts
 
@@ -39,7 +55,7 @@ NOTREADY@              ; Loop point for UART waiting
   lda UART_LSR         ; Wait for UART to be ready
   anda UARTF_LSR_THRE
   bne NOTREADY@
-  stb UART_BUFR        ; Actually do our write
+  stb UART_THR         ; Actually do our write
   bra OUTSTR           ; Reset for the next char
 END@                   ; Jump point for end of routine
   rts