uart-test.mu4

| This file is part of muforth: https://muforth.dev/
|
| Copyright 2002-2024 David Frech. (Read the LICENSE for details.)

loading PIC18 UART test code

hex

__meta

( Set config registers)
.ifdef 1xk50   | at the moment, the only option
   %0010_0010  ( CONFIG1H: FOSC=HS 0010)         CONFIG1H config-space c!
   %0001_1110  ( CONFIG2H: WDTEN=0)              CONFIG2H config-space c!
   %1100_0101  ( CONFIG4L: ENH_CPU=1)            CONFIG4L config-space c!
.then

boot
xinst on

4 org  ( skip reset jmp at 0, but clobber the IRQ handler slots!)

( Wait for RCIF, then read received byte into W)
label get-byte
   begin  PIR1 ) 5 ( RCIF) btstss  again  RCREG ) ldw  ret  ;c

( Wait for TXIF, then transmit W)
label put-byte
   begin  PIR1 ) 4 ( TXIF) btstss  again  TXREG ) stw  ret  ;c

( Stack pointed to by z is empty descending, so 0 ,z is scratch)
label process-serial
   get-byte c  put-byte c  ( echo)
   1 addi put-byte c
   1 addi put-byte c
   1 addi put-byte j  ;c

hooks RESET
label the-real-reset-starts-here
   ( UART TX is on RB7; set it as an output)
   TRISB ) 7 bclr

   | Also, RX, on pin RB5, is shared with AN11, to which - rather oddly -
   | it defaults at reset. So we reset ANS11 to claim the pin as a digital
   | input.
   ANSELH ) 3 bclr

   #12,000,000 #57,600 / #16 / 1- ldi  SPBRG ) stw
   %0010_0100 ldi  TXSTA ) stw  ( enable xmit, enable BRGH)
   %1001_0000 ldi  RCSTA ) stw  ( enable serial port, enable rcvr)

   #ram  1-  ldz  ( stack)
   begin  process-serial c  again  ;c