6 CLOCK MANAGEMENT UNIT (CMU)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
6-5
Selecting the PLL Input Clock
6.4.2
The PLL input clock can be selected from among 10 kinds of OSC3 divided clocks, OSC3/1 to OSC3/10, using
PLLINDIV[3:0]/CMU_PLLINDIV register.
4.2.1 PLL Input Clock (OSC3 Division Ratio) Selections
Table 6.
PLLINDIV[3:0]
Division ratio (OSC3/n)
0xf–0xa
1/8
0x9
1/10
0x8
1/9
0x7
1/8
0x6
1/7
0x5
1/6
0x4
1/5
0x3
1/4
0x2
1/3
0x1
1/2
0x0
1/1
(Default: 0x7)
Notes: • The PLL input clock can only be selected when the PLL is turned off (PLLPOWR/CMU_
PLLCTL0 register = 0) and the clock source is other than the PLL (CLKSEL[1:0]/CMU_OSC-
SEL register is not 0x2). If the PLL input clock is changed while the system is operating with
the PLL clock, the system may operate erratically.
• For the range of the input clock frequency, see “Electrical Characteristics.”
Setting the Frequency Multiplication Rate
6.4.3
The PLL frequency multiplication rate can be specified as shown in the table below using PLLN[3:0]/CMU_
PLLCTL0 register.
4.3.1 PLL Frequency Multiplication Rates
Table 6.
PLLN[3:0]
Multiplication rate
0xf
x16
0xe
x15
0xd
x14
0xc
x13
0xb
x12
0xa
x11
0x9
x10
0x8
x9
0x7
x8
0x6
x7
0x5
x6
0x4
x5
0x3
x4
0x2
x3
0x1
x2
0x0
x1
(Default: 0x0)
PLL output clock frequency = PLL input clock frequency
×
multiplication rate
Notes: • The frequency multiplication rate must be set so that the PLL output clock frequency does not
exceed the upper-limit operating clock frequency. For the multiplication rates that can be set
and the range of the output clock frequency, see “Electrical Characteristics.”
• The frequency multiplication rate can only be set when the PLL is turned off (PLLPOWR/
CMU_PLLCTL0 register = 0) and the clock source is other than the PLL (CLKSEL[1:0]/CMU_
OSCSEL register is not 0x2). If the frequency multiplication rate is changed while the system
is operating with the PLL clock, the system may operate erratically.