UART configuration

hi , i'm working on PHILIPS NXP LPC2378 device (ARM7TDMI )

and i'm trying to learn how to use the UART(universal asynchrone receiver/transmitter)
i found some difficulties in some of the registers such as :

- UnDLL
-UnDLM

i know that the two registers contains the value of the clock dividor , all that to define the baude rate clock , in other words the speed of the data transmission

but i have no idea about the values that i have to put into thoses registers
please if someone know something tell me more !!

thanks in advance !!

did you see datasheet? they have given the formula there see it once.

The sequence of events is pretty simple: set DLAB=1, set the baudrate (remember it's X16), then set DLAB=0...

Here's a piece of code to experiment with:

U0FDR = 0;/* Fractional divider not used*/
U0LCR = 0x83;/* DLAB = 1, 8 bits, no Parity, 1 Stop bit */ 
FreqDivisor = ( (double)(UART_frequency) / 16.0 ) / (double)(baudrate) ;
U0DLM = (UNS_32)(rint(FreqDivisor / 256.0));/* baud rate */						
U0DLL = (UNS_32)(rint(FreqDivisor)) % 256;
U0LCR = 0x03;/* DLAB = 0 */

thank you for your answers,

i would also know more about TXD0 and RXD0
can i use them like GPIO mode for simulationg sending and receiving data for exemple ??

I don't understand your question. Can you please rephrase it?

LPC series controller provides you option to select alternate function of a pin. this is generally done from PINSEL registers (see manual for more help). By default all pins are defined as GPIO. you can select alternate function by setting proper bits in respective PINSEL register for that GPIO.

look i'm trying to write a program which performs the following things :

-receive data , it means that the microcontroller have to receive an RS232 signal (start bit, the information, stop bit)
and put it into a buffer(memory )

so i asked if this information can be received by toggling the RXD0 of the UART0

thank u

well why you want to toggle yourself?? you have hardware UARTs... everything is done by hardware you get the final data in a register thats it. simple.. move it to buffer wherever you want.

look i'm trying to simulate receiving data , so toggling on RXD0 may be the solution no ??
and after the UART0 will put this information into RX FIFO , and to see it we can use U0RBR
that's it ??

if no please can you tell me the process to follow to perform my action , thank you

are you using a software to simulate? which one?
e.g if its proteus then you can connect a virtual terminal to it. If you're testing in Keil then you can open uart window and send data to controller just like a virtual terminal.

toggling RXD pin wont be a solution coz you wont be able to match the transfer baudrate.