HD6433044 Datasheet, PDF (520/867 Pages) Hitachi Semiconductor – Hitachi Single-Chip Microcomputer

14.3.5 Clock
As its serial communication clock, the smart card interface can use only the internal clock
generated by the on-chip baud rate generator. The bit rate can be selected by setting the bit rate
register (BRR) and bits CKS1 and CKS0 in the serial mode register (SMR). The bit rate can be
calculated from the equation given below. Table 14-5 lists some examples of bit rate settings.
If bit CKE0 is set to 1, a clock signal with a frequency equal to 372 times the bit rate is output
from the SCK₀ pin.
ø
B=
× 10⁶
1488 × 2^2n–1 × (N + 1)
where, N: BRR setting (0 ≤ N ≤ 255)
B: Bit rate (bits/s)
ø: System clock frequency (MHz)*
n: See table 14-4
Table 14-4 n-Values of CKS1 and CKS0 Settings
n
CKS1
CKS0
0
0
0
1
0
1
2
1
0
3
1
1
Note: * If the gear function is used to divide the system clock frequency, use the divided frequency
to calculate the bit rate. The equation above applies directly to 1/1 frequency division.
Table 14-5 Bit Rates (bits/s) for Different BRR Settings (when n = 0)
ø (MHz)
N
7.1424 10.00
10.7136 13.00
14.2848
0
9600.0 13440.9 14400.0 17473.1 19200.0
1
4800.0 6720.4
7200.0
8736.6
9600.0
2
3200.0 4480.3
4800.0
5824.4
6400.0
Note: Bit rates are rounded off to one decimal place.
16.00
21505.4
10752.7
7168.5
18.00
24193.5
12096.8
8064.5
510