Jonathan,

I have been toying with the USART of the 16c73a, with some limited
success. I'm new to this stuff so I don't know how much help I can be,
but some code fuctions and initialisation blocks are below, regardless.
Just a couple of points/questions first.

Why do you not initialise the data direction of your output pins? Is
this not required on you chip, or are trying to limit your posted code?

You do not need to be clearing TXREG after each byte sent. Once a new
value is loaded into the TXREG, it is transferred to the TSR register
one instruction later (provided of course the last value in the TSR has
been completely sent - otherwise, it sits there until TSR is empty).

You do not need to disable the transmitter in between bytes (for normal
operation - you may have something else going on). Only after a new
value is loaded into TXREG is it tranferred to the TSR register, so as
long as you are not putting new values in TXREG, nothing should
transmit.

Why do you include NOPs in your loop. I ask this one for myself. I have
found that looping simply on TRMT or TXIF (PIR1) does not work for some
reason (I have added a call to a simple delay myself). Is this your own
code hack, or did you receive a heads up on this from some literature or
perhaps somebody else?

I am collecting all the information I have on the USART so that I can
make a post on the PICLIST at some point, but it is still incomplete - I
hope this snip of info is helpful for now.

; Initialise PORTC (USART)
   BCF      STATUS, RP0        ; Bank 0 (PORTC)
   CLRF     PORTC              ; Clear output data latches
   BSF      STATUS, RP0        ; Bank 1 (TRISC)
   MOVLW    b'11000000'        ;
   MOVWF    TRISC              ; Set RC<5:0> as outputs
                               ; RC<7:6> as inputs, but really USART
TX/RX
                               ; (as per 16cxx specification sheet page
99)

; Initialise the UART
   BCF      STATUS, RP0        ; Bank 0 (RCSTA)
   MOVLW    0x90               ; SPEN=1, CREN=1
   MOVWF    RCSTA              ;
   BSF      STATUS, RP0        ; Bank 1 (SPBRG & TXSTA)
   MOVLW    0x09               ; BRG Control Value
   MOVWF    SPBRG              ;
   BSF      TXSTA, TXEN        ; Enable transmission (default is Async)

; Program code here ...

; Function requires value to be transmitted to be loaded into W BEFORE
this
;  function is called (be carefull not to over write value in
TRANS_DELAY)
UART_TRANS
   BSF      STATUS, RP0        ; Bank 0 (PIR1 & TXREG)
LOOP
   call     TRANS_DELAY
   BTFSS    PIR1, TXIF         ; TXIF=1 ? (= TXREG clear)
   GOTO     LOOP               ;
   NOP                         ;
   MOVWF    TXREG              ; Transmit value loaded into W before
                               ;  this function was called
   RETURN

If your chip does not required page/bank bits, ignore the 'Bank 0/1'
statements - if it does, be sure you are selecting the correct
page/bank. Actually, this whole post assumes that USARTs are
structurally the same between chips (a decent assumption, but I'm not
positive). It may be worth finding out if it is so.

Let me know how it goes.

Regards,

Mario

Jonathan ferguson wrote:
>
> Can some one Show me how to output, through the USART on a PIC17c43, say 2
> or 3 bytes of data one after another.  I can now output one byte but I can't
> get it to output more that one here's the code I've been playing with but
> all this does is crash my PC
>
> ##############################################################
> LIST   P=PIC17C43
>  #INCLUDE <P17C43.INC>
>
>   ORG 0
>
>                           MOVLW 0X4  ;INIT
>                           MOVWF SPBRG
>                           BCF TXSTA , SYNC
>                           BSF RCSTA , SPEN
>
>                           MOVLW 0X43  ;NEW DATA
>                           MOVWF TXREG  ;MOVE TO TXREG
>                           BSF TXSTA , TXEN ;SEND
> LOOP                NOP
>                           NOP
>                           NOP
>                           NOP
>                           NOP
>                           NOP
>                           NOP
>                           NOP
>                           BTFSS TXSTA , TRMT ;POLL TRMT TO SEE WHEN TSR IS
> EMPTY
>                           GOTO LOOP
>                           CLRF TXREG , F  ;NOT SURE IF THIS NEEDED
>                           BCF TXSTA , TXEN ;DISABLE SEND
>                           MOVLW 0X43  ;NEW DATA
>                           MOVWF TXREG  ;IN TXREG
>                           BSF TXSTA , TXEN ;SEND
>
>                           GOTO $
>
>                           END
>
> ######################################################################
>
> Thanks in advance
>
> Regards
>
> Jonathan Ferguson
> ------------------------------------------------------
> Research Student
> Microelectronics/Radiation Group
> University of  Lancaster
> Lancaster
> Bailrigg
> Lancs LA1 4YR
> Tel : (01524) 593326
> Fax :(01524) 381707
> j.ferguson@lancaster.ac.uk
> ICQ 31455174
>
> ----- Original Message -----
> From: Andy Kunz <support@MONTANADESIGN.COM>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Friday, September 03, 1999 2:04 PM
> Subject: [OT] Blatant Advertisement
>
> > This is blatant off-topic advertising, but just so you can see what I do
> in
> > my "spare" time.
> >
> > Not totally OT, though - it has a PIC in it (driving the speed
> > control/electronic throttle).
> >
> >         http://www.rc-hydros.com/videos.html
> >
> > Andy
> >
> > ==================================================================
> > Andy Kunz               Life is what we do to prepare for Eternity
> > ------------------------------------------------------------------
> > andy@rc-hydros.com      http://www.rc-hydros.com     - Race Boats
> > andy@montanadesign.com  http://www.montanadesign.com - Electronics
> > ==================================================================
> >