Mike Harrison says:
While we're on the subject of neat little routines etc...
This code sends a byte at 115.2Kbaud
With a 4.096MHZ xtal, error is about 1.25% (near enough),
with 4.000MHz, 4.55% (marginal).
Data is non-inverted (i.e can be fed straight to PC)txbyte movwf temp movlw d'10' ; 1 start + 8 data + 1 stop movwf cnt bcf status,c ;start bit movf portb,w txloop andlw 0ff-(1<<seroutbit) skpc iorlw 1<<seroutbit movwf portb sec rrf temp ; carry shifted in as stop bit decfsz cnt goto txloop return
Incidentally It's also possible to do 115K2 bit-bashed reception at 4.096MHz, by generating an INT interrupt off the startbit edge, and grabbbing all the data bits within the int code. Context save/restore overheads mean there's only a couple of cycles available to the foreground task if data is streaming in continuously!
|file: /Techref/microchip/rs232at115kbps.htm, 1KB, , updated: 2000/3/20 11:02, local time: 2020/3/30 00:58,
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<A HREF="http://www.massmind.org/Techref/microchip/rs232at115kbps.htm"> Mike Harrisons 115.2kBaud with a 4.096Mhz crystal</A>
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