Send serial value to change DS1620 values through PIC 16F628?

Hi!
I want to set TH and TL values in DS1620 through PIC 16F628 by serial.
In theory,

I want to send values to serial 16F628 and that these values change the TH and TL , or start or stop the conversion. Supposedly should be a protocol that sets the action which is to be performed, and must be included in the serial value.

Example: if I want to assign to the TH 40 degrees before 40 degrees must be some symbol or string that identifies this value (40 ) corresponds to TH . Something like this : serin portb.4 , N2400 , ' TH'40 but really do not know how it is done

someone can help me?,

How i can to do that?