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#use RS232 and Timer0

 
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hmn44
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#use RS232 and Timer0
PostPosted: Fri Sep 04, 2009 12:15 am     Reply with quote
May I use a timer0 interrupt and a software RS232 ?
In another way does the software RS232 use the timer0 ?
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Fri Sep 04, 2009 12:31 am     Reply with quote
Quote:
May I use a timer0 interrupt and a software RS232 ?

The timer interrupt will interfere with the bit timing of the software UART.
Use the DISABLE_INTS parameter in the #use rs232() statement to
prevent this.
http://www.ccsinfo.com/forum/viewtopic.php?t=36570


Quote:
In another way does the software RS232 use the timer0 ?

No. It uses software timing loops to create the time delays for the bits.
The CCS software UART code uses method #3 of making a software
UART, as listed on this page:
http://www.8052.com/faqs.phtml?FAQ=124758
hmn44
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PostPosted: Fri Sep 04, 2009 12:48 am     Reply with quote
Once more read the manual first ! many thanks
John P



Joined: 17 Sep 2003
Posts: 331

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PostPosted: Fri Sep 04, 2009 9:23 am     Reply with quote
Method 2 on the list is perfectly usable, and it lets you keep your timer running all the time (if you need that) and doesn't hog the processor. But if the timer is running that way, there will be "glitches" in its operation at the start of a received byte. And, it involves some non-trivial programming where having an oscilloscope to check timing can be helpful.
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