Solution:

As you know, we can set baudrate as 9600,19.2K, 38.4K, 57.6K and so on, but how about 76.8K? This baudrate can't be configurated because it is impossible to satisfy the following formula: BRD ( Baud Rate Divisor ) = frequency of oscillator / ( 16 x baudrate ) For example, if you use an oscillator with 1.8432MHz and want to set baudrate as 38.4K, then BRD = 1.8432M / ( 16 x 38.4K ) = 0003H That means you must set BRDH = 00H and BRDL = 03H in order to get 38.4K baudrate. From this viewpoint, you can figure out there is no way to set 76.8K baudrate. However, you can refer to the following ways to overcome this situation: 1. Change oscillator: Just like the above example, you can only change oscillator from 1.8432MHz to 3.6864MHz in order to achieve your goal. Actually, the keypoint is the formula. 2. High speed setting: Just like PCL-849 which adopts 14.7456MHz oscillator and allow you to set high speed ( x 8 ) mode, you can follow the below steps to complete it. step1: Set high speed ( x 8 ) mode step2: According to the above formula to calculate BRDH and BRDL in order to get 9600 baudrate. BRDH = 00H BRDL = 0CH step3: After that, the physical baudrate is 9600 x 8 = 76.8K