Hi,

I have a 16F876A transmitting via HSEROUT to a 18F4550 with a 20MHz crystal and I'd like to use the maximum speed possible.
http://ww1.microchip.com/downloads/e...Doc/39582b.pdf

I select High Speed (BRGH=1) on table 10.1 on p.115, so I only have the option of SYNC=0 (asynchronous). Asynchronous table 10-3 on p.116 gives a KBAUD rate of 312.5 for a 20 MHz speed and a SPBRG value 0.

I have absolutely no idea how they got from this formula FOSC/(16 (X + 1)) using the settings I chose. Anyways, how does this relate with the HSER_BAUD command? KBAUD means kilobaud in my mind, that would mean 312.5 x 1000, that value seems waaaaaay too high for me. I wasn't expecting anything higher than 115200 or so based on experience with modems.

I checked the datasheet for the 18F4550 (table 20-3 on p.245) and that's exactly the top end:
http://ww1.microchip.com/downloads/e...Doc/39632c.pdf

So now I'm confused on what setting to take to get the 2 chips working reliably. I'd really like to understand this 'cause I might have to change chip later.

Robert