Holtek HT66F20 Manual page 248

• Calculating the baud rate and error values
For a clock frequency of 4MHz, and with BRGH set to 0 determine the BRG register value N,
the actual baud rate and the error value for a desired baud rate of 4800.
From the above table the desired baud rate BR=
Re-arranging this equation gives N=
Giving a value for N=
To obtain the closest value, a decimal value of 12 should be placed into the BRG register. This
gives an actual or calculated baud rate value of
4000000
BR=
[64 (12+1)]
Therefore the error is equal to
The following tables show the actual values of baud rate and error values for the two value of
BRGH.
Baud
Rate f =4MHz
CLKI
K/BPS
BRG Kbaud
0.3 20� 0.300
�.2 5� �.202
2.4 25 2.404
4.8 �2 4.808
9.6 6 8.929
�9.2 2 20.833
38.4 — —
5�.6 0 62.500
��5.2 — —
Baud
Rate f =4MHz
CLKI
K/BPS
BRG Kbaud
0.3 — —
�.2 20� �.202
2.4 �03 2.404
4.8 5� 4.808
9.6 25 9.6�5
�9.2 �2 �9.23�
38.4 6 35.��4
5�.6 3 62.5
��5.2 � �25
250 0 250
Rev. 2.50
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
f
CLKI
(BR×64)
4000000
−1
=12.0208
(4800×64)
=4808
4808−4800
=0.16%
4800
Baud Rates for BRGH=0
f =3.579545MHz
CLKI
Error(%) BRG Kbaud
0.�6 �85 0.300
0.�6 46 �.�90
0.�6 22 2.432
0.�6 �� 4.66�
-6.99 5 9.32�
8.5� 2 �8.643
— — —
8.5� 0 55.930
— — —
Baud Rates and Error Values for BRGH=0
Baud Rates for BRGH=1
f =3.579545MHz
CLKI
Error(%) BRG Kbaud
— — —
0.�6 �85 �.203
0.�6 92 2.406
0.�6 46 4.�6
0.�6 22 9.�2�
0.�6 �� �8.643
-6.99 5 3�.286
8.5� 3 55.930
8.5� � ���.86
0 — —
Baud Rates and Error Values for BRGH=1
248
A/D Flash MCU with EEPROM
f
CLKI
[64 (N+1)]
−1
f =7.159MHz
CLKI
Error(%) BRG Kbaud
0.00 — —
-0.83 92 �.203
�.32 46 2.380
-2.90 22 4.863
-2.90 �� 9.322
-2.90 5 �8.643
— 2 32.286
-2.90 � 55.930
— 0 ���.859
f =7.159MHz
CLKI
Error(%) BRG Kbaud
— — —
0.23 — —
0.23 �85 2.406
-0.83 92 4.8��
�.32 46 9.520
-2.90 22 �9.454
-2.90 �� 3�.286
-2.90 � 55.930
-2.90 3 ���.86
— — —
Error(%)
—
0.23
-0.83
�.32
-2.90
-2.90
-2.90
-2.90
-2.90
Error(%)
—
—
0.23
0.23
-0.83
�.32
-2.90
-2.90
-2.90
—
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