gnupic: PIC16F877 & USART
Subject:
Re: PIC16F877 & USART
From:
Edward Tiong ####@####.####
Date:
28 Dec 2002 21:37:33 -0000
Message-Id: <3E0E17A8.A7A152F0@shaw.ca>
Take a look at this code at
http://www.ee.ualberta.ca/~ee401/debug/debug877.asm Actually, here is
the snipplet of code ...
; receives: nothing
; uses: W
; returns: nothing
;*******************************************************************
initializeUART ; Set up for hardware flow control
banksel BANK0 ; Set to bank0
bcf PORTC,Tx_PIN ; Initial condition for the Tx line
bcf PORTC,Rx_PIN ; Initial condition for the Rx line
bcf PORTB,RTS_PIN ; Initial condition for the RTS line
bsf PORTB,CTS_PIN ; Initial condition for the CTS line
banksel BANK1 ; Set to bank1
bsf TRISB,RTS_PIN ; set RTS Pin to input
bcf TRISB,CTS_PIN ; set CTS Pin to output
bsf TRISC,Tx_PIN ; set Rx and Tx Pins to default as
bsf TRISC,Rx_PIN ; high impedance
bcf PIE1,RCIE ; Disable uart interrupts
bcf PIE1,TXIE
; Set baud Rate to one of the following
; movlw 0xCF ; 300 baud
; movlw 0x67 ; 2400 baud
movlw 0x19 ; 9600 baud (see table in pic16f873.pdf)
; movlw 0xC ; 19200 baud
movwf SPBRG
movlw 0x24 ; Initialize Tx status and control register
movwf TXSTA
banksel BANK0 ; Set to bank0
movlw 0x90 ; Initialize Rx status and control register
movwf RCSTA
return
Or take a closer look at what the University of Alberta - Electrical and
Computer Engineering department is doing with the PIC16F873 and
PIC16F877. (http://www.ee.ualberta.ca/~ee041)
Please keep in mind that the PIC code written on this site was done by
students for students.
Hopefully this helps.
Rick Mann wrote:
>
> Hi. I'm trying to get a PIC16F877 to work at 9600 baud. It works fine at
> 2400, with BRGH=0, but I can't seem to get reliable operation at 9600 with
> BRGH=1.
>
> I thought I read somewhere that one shouldn't even try to use BRGH=1, but
> all of the examples I've seen on the Microchip website and Piclist.com seem
> to do it.
>
> FWIW, it seemed to work better when the SPRG value was set to 26 instead of
> 25, the value everything says I should use.
>
> I have a MAX232 from TI between the PIC and the PC. The handshaking lines
> are all hard-wired.
>
> I try to send ascii '0' through '9' from my terminal program, and display
> those values on 8 LEDs. At 2400 baud, it works great. At 9600, I get
> incorrect (although consistently) values.
>
> Any ideas? Thanks!
>
> --
> Rick
>
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