I recall the design spec of the RC Internal Osc is +-2.5% accross the operating temp range.... This was the orginal design breif.

Oh... yes, I just claculated from the data sheet.

RC Osc min - max MHz 7.189 7.557 (across the full temp range)
with the target centre freq at 7.3728MHz... which is -+2.5%.

Factory Trimed to within 1% at 25oC

What happens when you warm the LPC925? Do the errors reduce?

What are you connecting the LPC925 too? RS232 level coverter and a PC?

What baud rate are you using? 9600?

Here's an article from Maxim's web site which discusses baud rate error
http://www.maxim-ic.com/appnotes....umber/2141

If it is too cold or hot in Hamilton and you adjust the trim register... will you be adjusting a significant offset from the nominal at 25oC?

hat happens when you warm the LPC925? Do the errors reduce?

Todays weather in Hamilton is predicted as Max: 18.8 °C (4:39 PM)
Min: 15.2 °C (9:00 AM)

Is your receiving UART (PC or device ) withing specifications?

Side note
I did some tests years ago - where I sent square waves in to the serial port of PC (via an RS232 Level converter), varied the sig-gen to see when errors started apprearing in Hyper-terminal.

600 Hz = 1200baud (one positive transistion = 1logic, zero = 0logic). etc, buy adjusting off 600Hz we could measure when the serial port started sliping with errors. 'U' characters received.

Sorry I can't recall the results...


Just my 2 cents worth.

Joe

PS.... I can see from the Hamilton Internet Weather this month... it hasn't gone beyond 25oC.