R01UH0823EJ0100 Rev.1.00
Page 1435 of 1823
Jul 31, 2019
RX23W Group
40. SD Host Interface (SDHIa)
40.2.10 SDHI Clock Control Register (SDCLKCR)
Note 1. Bits CLKSEL[7:0] and CLKEN cannot be write accessed when the SDSTS2.SDCLKCREN flag is 0.
Note 2. When setting the CLKSEL[7:0] bits to 11111111b or when changing the CLKSEL[7:0] bit values from 11111111b to another
value, perform the following steps:
(1) Set the CLKEN bit to 0. Do not change the other bit values.
(2) Change the CLKSEL[7:0] bit values. Do not change the other bit values.
(3) Set the CLKEN bit to 1. Do not change the other bit values.
The SDCLKCR register controls the SDHI clock frequency settings and output. Set the CLKEN bit to 1 before writing to
the SDCMD register to start a command sequence. Do not write access the SDCLKCR register when the
SDSTS2.SDCLKCREN flag is 0.
CLKCTRLEN Bit (SDHI Clock Output Automatic Control Select)
The SDHI clock output automatic control is a function for starting and stopping SDHI clock output only during a
command sequence. When this function is enabled, the SDHI starts outputting the SDHI clock after a value is set to the
SDCMD register. After the command sequence is complete and eight cycles of the SDHI clock elapse, the SDHI stops
outputting the SDHI clock. When the SDCLKCR.CLKEN bit is 0, output from the SDHI_CLK pin becomes low
regardless of the CLKCTRLEN bit setting.
SDCLKCR
Address(es): SDHI.SDCLKCR 0008 AC48h
b31
b30
b29
b28
b27
b26
b25
b24
—
—
—
—
—
—
—
—
Value after reset:
0
0
0
0
0
0
0
0
b23
b22
b21
b20
b19
b18
b17
b16
—
—
—
—
—
—
—
—
Value after reset:
0
0
0
0
0
0
0
0
b15
b14
b13
b12
b11
b10
b9
b8
—
—
—
—
—
—
CLKCTRLEN
CLKEN
Value after reset:
0
0
0
0
0
0
0
0
b7
b6
b5
b4
b3
b2
b1
b0
CLKSEL[7:0]
Value after reset:
0
0
1
0
0
0
0
0
Bit
Symbol
Bit Name
Description
R/W
b7 to b0
SDHI Clock Frequency Select
b7
b0
0 0 0 0 0 0 0 0: PCLKB divided by 2
0 0 0 0 0 0 0 1: PCLKB divided by 4
0 0 0 0 0 0 1 0: PCLKB divided by 8
0 0 0 0 0 1 0 0: PCLKB divided by 16
0 0 0 0 1 0 0 0: PCLKB divided by 32
0 0 0 1 0 0 0 0: PCLKB divided by 64
0 0 1 0 0 0 0 0: PCLKB divided by 128
0 1 0 0 0 0 0 0: PCLKB divided by 256
1 0 0 0 0 0 0 0: PCLKB divided by 512
1 1 1 1 1 1 1 1: PCLKB
Only set the values listed above.
R/W
b8
SDHI Clock Output Control
0: SDHI clock output is disabled (SDHI_CLK signal fixed low)
1: SDHI clock output enabled
R/W
b9
SDHI Clock Output Automatic
Control Select
0: Automatic control of SDHI clock output disabled
1: Automatic control of SDHI clock output enabled
R/W
b31 to b10
—
Reserved
These bits are 0 when read and cannot be modified.
R