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3.2 Baud Rate Generator Programming
The baud rate generator (hereafter referred to as the BRG) of the SCC consists of
a 16-bit down counter, two 8-bit time constant registers, and an output divide-by-
two. The time constant for the BRG is programmed into WR12 (least significant
byte) and WR13 (most significant byte). The equation relating the baud rate to the
time constant is given below while Table 4 shows the time constants associated
with a number of popular baud rates when using the standard MPA-200 9.8304
MHz clock.
Time_Const=
Clock_Frequency
2&Baud_Rate&Clock_Mode
-2
Where:
Clock_Frequency = crystal frequency of 9.8304 MHz
Clock_Mode = value programmed in WR4
Baud_Rate = desired baud rate
Table 4 Time constants for common baud rates
(for 9.8304 Mhz Clock)
3FFEH
300 -------------------------
1FFEH
600 -------------------------
0FFEH
1200 ------------------------
07FEH
2400 ------------------------
03FEH
4800 ------------------------
01FEH
9600 ------------------------
00FEH
19200 -----------------------
007EH
38400
-----------------------
Baud Constant (Hex)Baud Rate
9 Quatech Inc., MPA-200/300 Manual