Two questions :

1.
In order to compute the baudrate, there is the following formula :

TH1 = (unsigned char) (256 - (clock / (16 * 12 * baudrate))); when SMOD=1

On website ressources, I've found an uart sample software where there is nearly the same formula :

TH1 = (unsigned char) (256 - (clock / (16L * 12L * baudrate)));

The only difference is the 16L instead 16 and 12L instead 12. What are the 'L' utility ?

2.
I've checked this formula and confirmed with the Keil website tool for baudrate computation and the formula is OK

I've a 20MHz clock and for 1200 bauds, I've TH1=169 (1197 bauds)

In order to test, I've wrote this :
while (1)
{
UART_Putchar("A");
}

It's should send a "A" character continuously on the terminal

With my first formula, nothing happens and with the second including the L, some irrelevants characters are continuously displayed...

Let me know your feelings...

Stephane