6 CLOCK MANAGEMENT UNIT (CMU)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
6-21
D1
PCLK1_EN: PCLK1 Clock Enable Bit
Enables or disables the PCLK1 clock supply.
1 (R/W): Enabled (on) (default)
0 (R/W): Disabled (off)
The PCLK1 clock is used to operate the modules listed below.
• Prescaler (PSC Ch.0)
• 8-bit programmable timer Ch.0, 2, 4, 6 (T8 Ch.0, 2, 4, 6)
• 16-bit PWM timer Ch.0, 1 (T16A5 Ch.0, 1)
• 16-bit audio PWM timer (T16P)
• Universal serial interface (USI)
• Serial interface Ch.0 (FSIO Ch.0)
• A/D converter (ADC10)
• I
2
S (I2S)
• Misc registers (MISC)
The PCLK1_EN default setting is 1, which enables the clock supply. If all the modules listed above can
be stopped, disable the clock supply by setting PCLK1_EN to 0 to reduce current consumption.
D0
GCLK_EN: GCLK Clock Enable Bit
Enables or disables the GCLK clock supply to the GE module.
1 (R/W): Enabled (on) (default)
0 (R/W): Disabled (off)
The GCLK_EN default setting is 1, which enables the clock supply. If the GE module can be stopped,
disable the clock supply by setting GCLK_EN to 0 to reduce current consumption.
System Clock Division Ratio Select Register (CMU_SYSCLKDIV)
Register name Address
Bit
Name
Function
Setting
Init. R/W
Remarks
System Clock
Division Ratio
Select Register
(CMU_
SYSCLKDIV)
0x300105
(8 bits)
D7–5 –
reserved
–
–
–
0 when being read.
D4
MCLKDIV
MCLK clock divider select
1 1/2
0 1/1
0
R/W Write-protected
D3
–
reserved
–
–
–
0 when being read.
D2–0 SYSCLKDIV
[2:0]
System clock division ratio select SYSCLKDIV[2:0] Division ratio
0x0 R/W Clock source =
OSC (OSC3, PLL,
or OSC1)
Write-protected
0x7–0x6
0x5
0x4
0x3
0x2
0x1
0x0
1/1
1/32
1/16
1/8
1/4
1/2
1/1
D[7:5]
Reserved
D4
MCLKDIV: MCLK Clock Divider Select Bit
Selects the main system clock.
1 (R/W): SYSCLK/2
0 (R/W): SYSCLK/1 (default)
MCLK is the main system clock for S1C33L26. This bit selects either SYSCLK (selected with SYS-
CLKDIV[2:0]) or its halved clock.
When using the SDRAMC in double frequency mode (MCLK : SDCLK = 1 : 2), MCLK should be set
to SYSCLK/2 (SYSCLK is used for the SDRAM clock).
D3
Reserved
D[2:0]
SYSCLKDIV[2:0]: System Clock Division Ratio Select Bits
Selects a division ratio to set the system clock frequency. To reduce current consumption, operate the
C33 PE Core and peripheral modules using the slowest possible clock speed.