Do PIC's allow letters as literals?  What value does it use for them Ascii
standard?

-----Original Message-----
From: Michael Rigby-Jones [mailto:mrjones@NORTELNETWORKS.COM]
Sent: Friday, December 08, 2000 9:04 AM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC]: Newbie PICster


> -----Original Message-----
> From: Duane Brantley [SMTP:Duane.Brantley@GENBAND.COM]
> Sent: Friday, December 08, 2000 1:09 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      [PIC]: Newbie PICster
>
> Hello all,
>
> This is my first attempt at using a PIC. I thought I'd start out simple
> and
> grow from there.  I tried writing a small program in MPASM to send the
> word
> "Hello" out the USART on a F877, but with no luck.  I was wondering if
> someone could take a look at it, and tell me what I'm doing wrong.
>
> Cheers,
> Duane
>
>
> ;========(HELLO.ASM)======================================================
> ==
> =======(12/4/00)=====
> ;This program will display the text "Hello" on the LCD.
> ;-------------------------------------------------------------------------
> --
> ---------------------
>         list    p=16f877
>         #include <p16f877.inc>
>         radix   hex
> ;-------------------------------------------------------------------------
> --
> ---------------------
> ;       cpu equates  (memory map)
> ;-------MAIN--------------------------------------------------------------
> --
> ---------------------
>
>                 org     0x000
> SETBAUD:        bcf     STATUS,RP1      ;
>                 bSf     STATUS,RP0      ; Bank 1
>                 movlw   0x81            ; Set Baud Rate to 9600
>                 movwf   SPBRG           ;
>                 movlw   0x26            ; 8-bit transmit, transmitter
> enabled
>                 movwf   TXSTA           ;
>                 bcf     TRISC,6         ; set RC6 as output
>                 bcf     PIE1,4          ; clear interrupt bit (TXIE)
>                 bcf     STATUS,RP0      ; Bank 0
>                 movlw   0x80            ;
>                 movwf   RCSTA           ; Serial port enabled
>                 goto    HELLO
>
> SERIAL: btfss   PIR1,4          ; wait for bit 4 = 1 (showing TXREG empty)
>                 goto    SERIAL          ;  <== I get stuck in a loop here
>                 nop
>                 movwf   TXREG
>                 return
>
> HELLO:          movlw   'H'             ; Send out 'Hello'
>                 movwf   TXREG
>                 call    SERIAL
>                 movlw   'e'
>                 movwf   TXREG
>                 call    SERIAL
>                 movlw   'l'
>                 movwf   TXREG
>                 call    SERIAL
>                 movlw   'l'
>                 movwf   TXREG
>                 call    SERIAL
>                 movlw   'o'
>                 movwf   TXREG
>                 end
>
>
You have to set the SPEN bit (bit 7 of register RCSTA) to enable the serial
port.  The datasheet also states that bits TRISC6 and TRISC7 have to be set,
i.e. configured as inputs.  However ISTR there was some quite heated debate
a while back on the list as to whether this was actualy required.

Regards

Mike

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