We are trying to run a net+50 at 33Mhz and are having trouble with one of the serial ports. The reason we are running at the slower speed is because we had a bad board layout and the system/memory is unstable at 44Mhz because of it. we are using an external ttl oscillator. I changed the define XTAL1_FREQUENCY to 33177600, and the define PLLTST_SELECT to SELECT_THE_XTAL1_INPUT. With the previous setup the following occurs. Serial port 1 used as a console at 9600 baud. This serial port works correctly. Measuring the baud rate on an oscilloscope shows error less than 0.2% Serial port 2 used to talk to a modem at 2400 baud. This serial port is off by 2.5% as measured by an oscilloscope. It makes no sense why the 9600 works and the 2400 does not. any help would be appreciated. I belive our net+50 version number is 24. -Blake
Are you using external crystal or oscilator ? does it work fine on 44Mhz (your board or Dev. Board) ? is it a problem of serial port 2 ? Have you tried 9600 on serial port 2 or 2400 on serial port 1 ? What kind of modem are you using ? Normaly it’s ok and even recommended to set the serial speed to the modem higher then the actual baud rate between modems.