The following equation calculates the bit rate register (BRR) setting from the system clock
frequency and bit rate. N is an integer from 0 to 255, specifying the value with the smaller error.
N =
×
10
6
– 1
Table 14-6 BRR Settings for Typical Bit Rate (bits/s) (when n = 0)
ø (MHz)
7.1424
10.00
10.7136
13.00
14.2848
16.00
18.00
Bit/s
N
Error
N
Error
N
Error
N
Error
N
Error
N
Error
N
Error
9600
0
0.00
1
30.00
1
25.00
1
8.99
1
0.00
1
12.01
2
15.99
Table 14-7 Maximum Bit Rates for Various Frequencies (Smart Card Interface)
ø (MHz)
Maximum Bit Rate (bits/s)
N
n
7.1424
9600
0
0
10
13441
0
0
10.7136
14400
0
0
13
17473
0
0
14.2848
19200
0
0
16
21505
0
0
18
24194
0
0
The bit rate error is calculated from the following equation.
Error (%) =
×
10
6
–1
×
100
ø
1488
×
2
2n–1
×
B
ø
1488
×
2
2n – 1
×
B
×
(N + 1)
511
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