451
14.2.9
Bit Rate Register (SCBRR)
The bit rate register (SCBRR) is an 8-bit register that, together with the baud rate generator clock
source selected by the CKS1 and CKS0 bits in the serial mode register (SCSMR), determines the
serial transmit/receive bit rate.
The CPU can always read and write to SCBRR. SCBRR is initialized to H'FF by a reset, and in
module standby or standby mode. Each channel has independent baud rate generator control, so
different values can be set in two channels.
Bit:
7
6
5
4
3
2
1
0
Initial value:
1
1
1
1
1
1
1
1
R/W:
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
The SCBRR setting is calculated as follows:
Asynchronous mode: N
=
P
φ
64
×
2
2n – 1
×
B
×
10
6
– 1
Synchronous mode: N
=
P
φ
8
×
2
2n – 1
×
B
×
10
6
– 1
B:
Bit rate (bits/s)
N:
SCBRR setting for baud rate generator (0
≤
N
≤
255)
P
φ
: Operating frequency for peripheral modules (MHz)
n:
Baud rate generator clock source (n
=
0, 1, 2, 3) (for the clock sources and values of
n, see table 14.3.)
Table 14.3
SCSMR Settings
SCSMR Settings
n
Clock Source
CKS1
CKS0
0
P
φ
0
0
1
P
φ
/4
0
1
2
P
φ
/16
1
0
3
P
φ
/64
1
1
Note:
The bit rate error in asynchronous is given by the following formula:
Error (
%
)
= (
P
φ ×
10
6
(N + 1)
×
B
×
64
×
2
2n – 1
) ×
100
Содержание SH7709S
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