6 CLOCK MANAGEMENT UNIT (CMU)
6-16
Seiko Epson Corporation
S1C33L26 TECHNICAL MANUAL
Control Register Details
6.10
10.1 List of CMU Registers
Table 6.
Address
Register name
Function
0x300100 CMU_OSCSEL
Clock Source Select Register
Select system clock source
0x300101 CMU_OSCCTL
Oscillation Control Register
Control oscillators
0x300103 CMU_LCLKDIV
LCDC Clock Division Ratio Select Register
Set LCLK frequency
0x300104 CMU_CLKCTL
Clock Control Register
Control clock supply to peripheral/bus modules
0x300105 CMU_SYSCLKDIV System Clock Division Ratio Select Register
Set system clock frequency
0x300106 CMU_CMUCLK
CMU_CLK Select Register
Select CMU_CLK output clock
0x300107 CMU_PLLINDIV
PLL Input Clock Division Ratio Select Register Set PLL input clock frequency
0x300108 CMU_PLLCTL0
PLL Control Register 0
Set PLL multiplication rate and enable PLL
0x300109 CMU_PLLCTL1
PLL Control Register 1
Set PLL parameters
0x30010a CMU_PLLCTL2
PLL Control Register 2
0x30010c CMU_SSCG0
SSCG Macro Control Register 0
Enable SSCG
0x30010d CMU_SSCG1
SSCG Macro Control Register 1
Set SSCG parameters
0x300110 CMU_PROTECT
CMU Write Protect Register
Enable/disable CMU register write protection
The CMU module registers are described in detail below. These are 8-bit registers.
Notes: • When data is written to the registers, the “Reserved” bits must always be written as 0 and not 1.
• The CMU control registers at addresses 0x300100–0x30010d are write-protected. Before the
CMU control registers can be rewritten, write protection of these registers must be removed
by writing data 0x96 to CMUP[7:0]/CMU_PROTECT register. Note that since unnecessary re-
writes to the CMU control registers could lead to erratic system operation, CMUP[7:0] should
be set to other than 0x96 unless the CMU control registers must be rewritten.
Clock Source Select Register (CMU_OSCSEL)
Register name Address
Bit
Name
Function
Setting
Init. R/W
Remarks
Clock Source
Select Register
(CMU_OSCSEL)
0x300100
(8 bits)
D7–2 –
reserved
–
–
–
0 when being read.
D1–0 CLKSEL
[1:0]
System clock source select
CLKSEL[1:0]
Clock source
0x0 R/W Write-protected
0x3
0x2
0x1
0x0
Not allowed
PLL
OSC1
OSC3
D[7:2]
Reserved
D[1:0]
CLKSEL[1:0]: System Clock Source Select Bits
Selects the system clock source.
10.2 System Clock Source Selections
Table 6.
CLKSEL[1:0]
Clock source
0x3
Reserved
0x2
PLL
0x1
OSC1
0x0
OSC3
(Default: 0x0)
Note: Do not select the system clock from deactivated clock sources. It will cause the system to hang as
the CMU does not include a protection mechanism against such system clock selection.