piclist 2003\03\02\221705a >
Thread: More on UART
face BY : David Duffy email (remove spam text)

Tony N wrote:
>I've just been porting some code from an 873 to a 628 chip that uses the
>UART and found that the UART didn't work after the conversion.
>After some searching I found that I forgot to take out some code the
>sets TRISA and TRISB to 0x00.
>Now it does work.
>This suggests that TRISB does affect the UART whether the data sheet
>says otherwise.
>The PORTB UART diagram seems the same as for 87x series which indicates
>that enabling the UART overrides the TX RX pin settings.
>But....as with the 87x series, in the UART section it specifically
>mentions that TRISB<1:2> or TRISC<6:7> have to be set with SPEN to
>enable the UART.

Taken straight from a working product:

movlw           b'11111011'
movwf           tris_b

I did find that it didn't work when I originally (accidently) had TX set
to input and RX set to output. I don't recall whether it was only the
TX or RX that didn't work when the bits were flipped, or both.
I wonder if it makes any difference whether you do the UART setup
before the TRIS. (I do TRIS first, then the UART a few lines later)

David Duffy        Audio Visual Devices P/L
U8, 9-11 Trade St, Cleveland 4163 Australia
Ph: +61 7 38210362   Fax: +61 7 38210281
New Web: http://www.audiovisualdevices.com.au

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Subject (change) More on UART

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