6 CLOCK MANAGEMENT UNIT (CMU)
6-2
Seiko Epson Corporation
S1C33L26 TECHNICAL MANUAL
CMU Pins
6.2
Table 6.2.1 lists the input/output pins for the CMU module.
2.1 List of CMU Pins
Table 6.
Pin name
I/O
Qty
Function
RTCCLKI
I
1
OSC1 oscillator input pin
Connect a crystal resonator (32.768 kHz), a feedback resistor, and a gate capaci-
tor. Or input an external clock.
RTCCLKO
O
1
OSC1 oscillator output pin
Connect a crystal resonator (32.768 kHz), a feedback resistor, a drain resistor,
and a drain capacitor.
MCLKI
I
1
OSC3 oscillator input pin
Connect a crystal or ceramic resonator (max. 48 MHz), a feedback resistor, and a
gate capacitor. Or input an external clock.
MCLKO
O
1
OSC3 oscillator output pin
Connect a crystal or ceramic resonator (max. 48 MHz), a feedback resistor, a
drain resistor, and a drain capacitor.
CMU_CLK
O
1
CMU_CLK output pin
Outputs the clock selected from OSC3, OSC1, PLL, OSC/1–OSC/32, and LCLK.
The CMU output pin (CMU_CLK) is shared with an I/O port and are initially set as general purpose I/O port pin.
The pin function must be switched using the port function select bit to use the general purpose I/O port pin as the
CMU output pin. For detailed information on pin function switching, see the “I/O Ports (GPIO)” chapter.
Oscillators
6.3
OSC3 Oscillator Circuit
6.3.1
The OSC3 oscillator circuit generates the main clock for high-speed operation of the C33 PE Core and peripheral
circuits.
Structure of the OSC3 oscillator circuit
The OSC3 oscillator circuit accommodates a crystal/ceramic oscillator and external clock input.
Figure 6.3.1.1 shows the structure of the OSC3 oscillator circuit.
Oscillation circuit
control signal
SLEEP control
Oscillation circuit
control signal
SLEEP control
V
SS
MCLKO
MCLKI
C
D3
C
G3
X'tal3
or
Ceramic
OSC3 clock
MCLKO
MCLKI
External
clock
N.C.
V
SS
LV
DD
OSC3 clock
(1) Crystal/ceramic oscillation circuit
(2) External clock input
R
f
R
d
3.1.1 OSC3 Oscillator Circuit
Figure 6.
For use as a crystal or ceramic oscillator circuit, connect a crystal (X’tal3) or ceramic resonator and a feedback
resistor (R
f
), two capacitors (C
G3
, C
D3
) and, if necessary, a drain resistor (R
d
) to the MCLKI and MCLKO pins
and V
SS
.
To use an external clock, leave the MCLKO pin open and input a LV
DD
-level clock (with a 50% duty cycle) to
the MCLKI pin.
The range of oscillation frequencies is as follows:
• Crystal oscillator:
5 MHz (min.) to 48 MHz (max.)
• Ceramic oscillator: 5 MHz (min.) to 48 MHz (max.)
• External clock input: 5 MHz (min.) to 48 MHz (max.)
• A 48 MHz clock source with 0.25% of accuracy should be connected for using the USB function.
• Before using a ceramic resonator, please be sure to contact Murata Manufacturing Co., Ltd. for further infor-
mation on conditions of use for ceramic resonators.
For details of oscillation characteristics and external clock input characteristics, see “Electrical Characteristics.”