R01UH0823EJ0100 Rev.1.00
Page 1347 of 1823
Jul 31, 2019
RX23W Group
38. Serial Peripheral Interface (RSPIa)
38.2.8
RSPI Bit Rate Register (SPBR)
SPBR sets the bit rate in master mode. Do not change the SPBR register while both the SPCR.MSTR and SPCR.SPE bits
are 1.
When the RSPI is used in slave mode, the bit rate depends on the bit rate of the input clock (bit rate satisfying the
electrical characteristics should be used) regardless of the settings of SPBR and the SPCMDm.BRDV[1:0] bits (bit rate
division setting bits).
The bit rate is determined by combinations of the SPBR setting and the SPCMDm.BRDV[1:0] bit setting. The equation
for calculating the bit rate is given below. In the equation, n denotes an SPBR setting (0, 1, 2, …, 255), and N denotes a
BRDV[1:0] bit setting (0, 1, 2, 3).
lists examples of the relationship among the SPBR settings, the BRDV[1:0] settings, and bit rates.
Use the bit rate that meets electrical characteristics based on the AC specifications of the target device.
Table 38.3
Relationship among SPBR Settings, BRDV[1:0] Settings, and Bit Rates
Address(es): RSPI0.SPBR 0008 838Ah
b7
b6
b5
b4
b3
b2
b1
b0
Value after reset:
1
1
1
1
1
1
1
1
SPBR (n)
BRDV[1:0] Bits (N)
Division
Ratio
Bit Rate
PCLK = 32 MHz
0
0
2
16.0 Mbps
1
0
4
8.00 Mbps
2
0
6
5.33 Mbps
3
0
8
4.00 Mbps
4
0
10
3.20 Mbps
5
0
12
2.67 Mbps
5
1
24
1.33 Mbps
5
2
48
667 kbps
5
3
96
333 kbps
255
3
4096
7.81 kbps
Bit rate
f PCLK
2
n 1
+
2
N
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