RX610 Group
20. Serial Communications Interface (SCI)
R01UH0032EJ0120 Rev.1.20
Page 632 of 1006
Feb 20, 2013
20.2.9
Bit Rate Register (BRR)
Addresses: SCI0.BRR 0008 8241h, SCI1.BRR 0008 8249h, SCI2.BRR 0008 8251h, SCI3.BRR 0008 8259h
SCI4.BRR 0008 8261h, SCI5.BRR 0008 8269h, SCI6.BRR 0008 8271h
b7
b6
b5
b4
b3
b2
b1
b0
Value after reset:
1
1
1
1
1
1
1
1
BRR is an 8-bit register that adjusts the bit rate.
As the SCI performs baud rate generator control independently for each channel, different bit rates can be set for each
channel. Table 20.5 shows the relationships between the N setting in BRR and bit rate B for normal asynchronous mode
and clock synchronous mode, and smart card interface mode.
The initial value of BRR is FFh.
BRR can be read from by the CPU at all times, but it can be written to only when the TE and RE bits in SCR are 0.
Table 20.5 Relationships between N Setting in BRR and Bit Rate B
Mode
Asynchronous
Clock synchronous
Smart card interface
N =
ABCS Bit in SEMR
−
1
Error (%) = {
−
1 }
×
100
BRR Setting
Error
0
1
64
×
2
2n
−
1
×
B
PCLK
×
10
6
N =
−
1
32
×
2
2n
−
1
×
B
PCLK
×
10
6
N =
−
1
8
×
2
2n
−
1
×
B
PCLK
×
10
6
N =
−
1
S
×
2
2n+1
×
B
PCLK
×
10
6
PCLK
×
10
6
B
×
64
×
2
2n
−
1
×
(N+1)
Error (%) = {
−
1 }
×
100
PCLK
×
10
6
B
×
32
×
2
2n
−
1
×
(N+1)
Error (%) = {
−
1 }
×
100
PCLK
×
10
6
B
×
S
×
2
2n+1
×
(N+1)
[Legend]
B:
Bit rate (bps)
N:
BRR setting for baud rate generator (0
≤
N
≤
255)
PCLK: Operating frequency (MHz)
n and S: Determined by the SMR setting shown in the following table.
SMR Setting
Clock Source
n
CKS[1:0] bps
0 0
PCLK clock
0
0 1
PCLK/4 clock
1
1 0
PCLK/16 clock
2
1 1
PCLK/64 clock
3