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chingB
Joined: 29 Dec 2003
Posts: 81
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| Framing and Overrun Error on Serial Comm |
 Posted: Mon Jun 28, 2004 5:10 pm |
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Hello,
Anyone in the community who can explain the cause and effect of serial framing error and overrun error.
How can I prevent a framing and overrun error ?
What will happend to #int_rda interrupt if framing error and/or overrun error will occur?
How can I add an error traper in my PIC such that it will not hung my interrupt? A sample code snippet will do...
BTW, where is the best way to put this error trapper for framing and overrun error?
I need ur help on this... I plan to use PIC18F1320.
Thnx |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Jun 28, 2004 5:42 pm |
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| Quote: | | How can I prevent a framing and overrun error ? |
To prevent framing errors, use the correct baud rate. Make sure it's
accurate. To prevent overrun errors, make sure you read a
character from the USART often enough so that the small internal
fifo doesn't overflow (it's only 2 characters deep). If you are using
an interrupt driven receive fifo, then don't disable interrupts for an
extended period of time.
| Quote: | | What will happen to #int_rda interrupt if framing error and/or overrun error will occur? |
It will lock up unless you clear the error.
| Quote: | | How can I add an error traper in my PIC such that it will not hung my interrupt? A sample code snippet will do... |
Simply add ERRORS to the end of your #use rs232() statement.
| Quote: | | BTW, where is the best way to put this error trapper for framing and overrun error? |
The best place is at the end of your #use rs232 statement.
Like this:
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS) |
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chingB
Joined: 29 Dec 2003
Posts: 81
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| Posted: Mon Jun 28, 2004 5:56 pm |
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which is better in handling errors... adding ERRORS at #use rs232() built-in function or by simply using register?
Thnx |
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Ttelmah
Guest
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| Posted: Tue Jun 29, 2004 6:32 am |
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| chingB wrote: | which is better in handling errors... adding ERRORS at #use rs232() built-in function or by simply using register?
Thnx |
In 'quality', no difference really.
However in 'code size', probably the latter.
As it stands, the 'errors' function, adds an error check to every getc, and then if an error is found, flags it, and clears it. If you want to perform your own code when an error is seen, you then have to test for the flag, and perform your code. Hence the test becomes duplicated when using the errors ability this way.
Also seperately, if for any reason, you disable the receive interrupt, and clear it, then the 'getc' won't be called, so in this case, manual clearing becomes essential.
For users who just want to ensure that the errors are cleared, and are using the I/O in a normal manner, the errors ability is fine (though adds in this case a couple of extra instructions to set the error flag, compared to a simple clear).
Best Wishes |
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Guest
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| Posted: Tue Jun 29, 2004 5:19 pm |
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| Ttelmah wrote: | | chingB wrote: | which is better in handling errors... adding ERRORS at #use rs232() built-in function or by simply using register?
Thnx |
In 'quality', no difference really.
However in 'code size', probably the latter.
As it stands, the 'errors' function, adds an error check to every getc, and then if an error is found, flags it, and clears it. If you want to perform your own code when an error is seen, you then have to test for the flag, and perform your code. Hence the test becomes duplicated when using the errors ability this way.
Also seperately, if for any reason, you disable the receive interrupt, and clear it, then the 'getc' won't be called, so in this case, manual clearing becomes essential.
For users who just want to ensure that the errors are cleared, and are using the I/O in a normal manner, the errors ability is fine (though adds in this case a couple of extra instructions to set the error flag, compared to a simple clear).
Best Wishes |
Do you have a sample snippet on using register for handling errors?
thnx |
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