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Automatic checksum

 
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gjs_rsdi



Joined: 06 Feb 2006
Posts: 468
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Automatic checksum
PostPosted: Mon Mar 04, 2019 2:05 am     Reply with quote

I am reading the data sheet of PIC18F27K42 and found in two places written that it has Automatic checksum for the UART module.

I didn't find explanation about it in the data sheet, how it works, etc.
I am missing something?

Best wishes
Joe
Ttelmah



Joined: 11 Mar 2010
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PostPosted: Mon Mar 04, 2019 2:48 am     Reply with quote

Clear the U0TXCHK register. Then set the C0EN bit in the UART.
Then send data, and the U0TXCHK register will contain the sum generated.
You read the byte in U0TXCHK, invert it, and send this as the last byte
after your data.
On receive, do the same, except clear the U0RXCHK register.
After the data is received, read U0RXCHK, add one to this. If the result
is zero, the checksum is OK.
If you are using 7bit mode you have to set bit 7 of the value before adding.
gjs_rsdi



Joined: 06 Feb 2006
Posts: 468
Location: Bali

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PostPosted: Mon Mar 04, 2019 3:45 pm     Reply with quote

Thank you Ttelmah, always helpful answers Smile

Best wishes
Joe
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