SH7262/SH7264 Group
Hardware Design Guide
REJ06B0999-0100 Rev. 1.00
Page 15 of 36
Jun. 30, 2010
4.2
Clock Operating Modes
4.2.1
External Pins Setting to Decide Clock Operating Modes
When the RES# pin is driven low, the SH7264 uses external pins to decide clock operating modes.
Table 5 lists the relationship between external pins and clock operating modes.
Table 5 Relationships between External Pins and Clock Operating Modes
Pin Combination
Clock I/O
Mode
MD_CLK1 MD_CLK0 Source
Output
Divider
1
PLL
Circuit
CKIO Frequency
0
0
0
EXTAL/crystal
CKIO
1
ON (×12)
(EXTAL/crystal) × 4
1 0
1
USB_X1/crystal
CKIO
1/4 ON
(×12)
(USB_X1/crystal)
2
1
0
EXTAL/crystal
CKIO
1
ON (×8)
(EXTAL/crystal) × 4
3
1
1
USB_X1/crystal
CKIO
1/3
ON (×8)
(USB_X1/crystal) × 4/3
4.2.2 Mode
0
Mode 0 provides the clock from the EXTAL pin or a crystal resonator. PLL circuit shapes the waveform and multiplies
the frequency to supply the clock to the SH7264. EXTAL pin input clock and crystal resonator within the range of
10 MHz and 12 MHz can be used in mode 0. The CKIO frequency range is 40 MHz to 48 MHz. When the USB 2.0
host or function module is not used, fix the EXTAL pin (connect to pull-up or pull-down resistors, connect to the power
supply or ground) and leave the USB_X2 pin open to reduce the power consumption.
4.2.3 Mode
1
Mode 1 provides the clock from the USB_X1 pin or a crystal resonator. PLL circuit shapes the waveform, sets the
Frequency control register (FRQCR) to multiply the frequency, and supplies the clock to the SH7264. The CKIO
frequency range is (USB_X1/crystal) (48 MHz). To reduce the power consumption, fix the EXTAL pin (connect to
pull-up or pull-down resistors, connect to the power supply or ground) and leave the XTAL pin open when using the
SH7264 in mode 1.
4.2.4 Mode
2
Mode 2 provides the clock from EXTAL pin or a crystal resonator. PLL circuit shapes the waveform and multiplies the
frequency to supply the clock to the SH7264. EXTAL pin input clock and crystal resonator within the range between
10 MHz and 18 MHz can be used in mode 2. The CKIO frequency range is 40 MHz to 72 MHz. When the USB 2.0
host or function module is not used, fix the USB_X1 pin (connect to pull-up or pull-down resistors, connect to the
power supply or ground), and leave the USB_X2 pin open to reduce the power consumption.
4.2.5 Mode
3
Mode 3 provides the clock from the USB_X1 pin or a crystal resonator. PLL circuit shapes the waveform, sets the
FRQCR to multiply the frequency, and supplies the clock to the SH7264. The CKIO frequency range is
(USB_X1/crystal resonator) × 4/3 (64 MHz). To reduce the power consumption, fix the EXTAL pin (connect to pull-up
or pull-down resistors, connect to the power supply or ground), and leave the XTAL pin open when using the SH7264
in mode 3.
