Oscillator Circuit; Example Of An Oscillator Circuit - Mitsubishi Electric M32R Series User Manual

18

18.1 Oscillator Circuit

The M32R/E contains an oscillator circuit that supplies operating clocks for the CPU core, internal
peripheral I/O, and internal memory. The frequency fed to the clock input pin (XIN) is multiplied by
4 by the internal PLL circuit to produce the CPU clock, which is the operating clock for the CPU core
and internal memory. The frequency of this clock is divided by 2 in the subsequent circuit to
produce the internal peripheral clock, which is the operating clock for the internal peripheral I/O.

18.1.1 Example of an Oscillator Circuit

A clock generating circuit can be configured by connecting a ceramic (or crystal) resonator between
the XIN and XOUT pins external to the chip. Figure 18.1.1 below shows an example of a system
clock generating circuit using a resonator connected external to the chip and an RC network
connected to the PLL circuit control pin (VCNT). For constants Rf, CIN, COUT, and Rd, consult
your resonator manufacturer to determine the appropriate values.
When you use an externally sourced clock signal without using the internal oscillator circuit,
connect the external clock signal to the XIN pin and leave the XOUT pin open.
OSCVSS OSCVCC
Figure 18.1.1 Example of a System Clock Generating Circuit
M32R/E
Oscillator module
Oscillator
circuit
XIN
XOUT
Rf
Rd
C
C
C
IN
OUT
18-2
OSCILLATION CIRCUIT
18.1 Oscillator Circuit
PLL circuit 1/2
VCNT
BCLK / P70
220pF
Ω
1K
0.1µF
OSCVCC : 3.3 V power supply
To CPU clock
To internal
peripheral
clock
Ver.0.10