6 CLOCK MANAGEMENT UNIT (CMU)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
6-1
Clock Management Unit (CMU)
6
CMU Module Overview
6.1
The CMU module controls the internal oscillators and the system clock.
The features of the CMU module are listed below.
• Generates the operating clocks with the built-in oscillators.
- OSC3 oscillator circuit: 48 MHz (max.) crystal or ceramic oscillator circuit
Supports an external clock input.
- OSC1 oscillator circuit: 32.768 kHz (typ.) crystal oscillator circuit
Supports an external clock input.
• Switches the system clock. The system clock source can be selected from OSC3, PLL, and OSC1 with software.
• Controls PLL and SSCG.
• Generates the system clock by dividing the source clock by 1 to 32.
• Generates the CPU core clock (CCLK) by dividing the system clock by 1 to 8.
• Controls the clock supply to the peripheral modules.
• Controls the clocks according to the standby mode (HALT, or SLEEP).
• Controls a clock output to external devices.
To reduce current consumption, control the clock in conjunction with processing and use standby mode. For more
information on reducing current consumption, see “Power Saving” in the appendix chapter.
Figure 6.1.1 shows the clock system and CMU module configuration.
OSC3
oscillator
(48 MHz)
OSC1
oscillator
(32.768 kHz)
Reset/NMI
control
NMI
RESET
CMU
WDT
#NMI
#RESET
MCLKI
MCLKO
OSC3
OSC1
PLL
OSC
CLKSEL[1:0]
CCLK
HALT
SLEEP
Wakeup
Power down
control
Gate
To C33 PE Core
CMU_CLK
RTCCLKI
RTCCLKO
RTC
WAKEUP
#STBY
Divider
(1/1–1/32)
Gate
Gate
C33 PE Core, IRAM, Cache
GE
LCDC
SAPB, Bus, DMAC, DSTRAM,
IVRAM, LCDC-AHB, CMU,
SRAMC_SDRAMC-AHB
T8 Ch.1/3/5/7, USIL, FSIO Ch.1,
WDT, PSC Ch.1, GPIO, BBRAM,
ITC, REMC,
CCU/SRAMC/SDRAMC/LCDC/
RTC registers
T8 Ch.0/2/4/6, ADC10, USI,
FSIO Ch.0, T16A5 Ch.0/1, I2S,
T16P, MISC, PSC Ch.0
CMU_CLKSEL[4:0]
PCLK2
Gate
USB registers
USBREGCLK
LCLK
Gate
PCLK1
SYSCLK
Gate
GCLK
USB
Gate
Gate
USBCLK
SRAMC_SDRAMC
Gate
SDCLK
Gate
BCLK
BCLK
LCLK
OSC/1–OSC/32
OSC1
PLL
OSC3
OSC/PLL/
SSCG
control
MCLKDIV
MCLK
1/2
PLL
x1–x16
(20–72 MHz)
SSCG
Wait
control
Divider
(1/1–1/10)
Divider
(1/1–1/32)
Divider
(1/1–1/8)
1.1 CMU Module Configuration
Figure 6.
Note: 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 rewrites
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.