CHAPTER 6 BUS CONTROL
User’s Manual U14272EJ3V0UM
117
6.2.6 CLKSPEEDREG (0x0A00 0018)
Bit
15
14
13
12
11
10
9
8
Name
DIV2
DIV3
DIV4
Reserved
Reserved
Reserved
Reserved
Reserved
R/W
R
R
R
R
R
R
R
R
Bit
7
6
5
4
3
2
1
0
Name
Reserved
Reserved
Reserved
CLKSP4
CLKSP3
CLKSP2
CLKSP1
CLKSP0
R/W
R
R
R
R
R
R
R
R
Bit
Name
Function
15 to 13
DIV(2:4)
Value used to calculate the TClock, MBA clock, and SDCLK operating frequency
12 to 5
Reserved
0 is returned when read
4 to 0
CLKSP(4:0)
Value used to calculate the CPU core operating clock (PClock) frequency
The following expression is used to calculate the PClock and TClock frequency:
(1) CPU core clock (PClock)
PClock = (18.432 MHz / CLKSP(4:0)) x 64
(2) Peripheral clock (TClock)
DIV(2:4)
Ratio
Mode
111
TClock = PClock / 1
Div1 mode
011
TClock = PClock / 2
Div2 mode
101
TClock = PClock / 3
Div3 mode
Others
Reserved
−
Remark
PClock frequency is decided by CLKSEL(2:0) pin statuses during RTC reset.
TClock frequency is always a half of PClock frequency (Div2 mode) immediately after RTC reset.
Software can change TClock Div mode by setting the PMUDIVREG register (0x0B00 00AC). A
change becomes valid when the V
R
4181 restores from the Hibernate mode after setting the
PMUDIVREG register.