SH7011 Datasheet, PDF (50/292 Pages) Renesas Technology Corp – CMOS single-chip microprocessors

Section 4 Clock Pulse Generator (CPG)
4.1 Overview
The clock pulse generator (CPG) supplies clock pulses within the SH7011 and to external devices.
The SH7011’s CPG operates the SH7011 at a frequency equal to the oscillation frequency of the
crystal resonator. The CPG is composed of an oscillator and a duty adjustment circuit (figure 4.1).
There are two ways of generating a clock with the CPG: by connecting a crystal resonator, or by
inputting an external clock.
XTAL
EXTAL
Oscillator
CPG
Duty adjustment
circuit
Internal
clock (φ)
CK (system
clock)
Figure 4.1 CPG Block Diagram
4.2 Clock Source
Either a crystal resonator or an external clock can be selected as the clock pulse source.
4.2.1 Crystal Resonator Connection
Circuit Configuration: Figure 4.2 shows the method of connecting a crystal resonator. Use the
damping resistance (Rd) shown in table 4.1. An AT-cut parallel-resonance type crystal resonator
with the same frequency as the system clock (CK) should be used. Load capacitors (C_L1, C_L2) must
be connected as shown in the figure.
The clock pulses generated by the crystal resonator and internal oscillator are sent to the duty
adjustment circuit. After the duty has been adjusted, the pulses are supplied within the SH7011
chip and to external devices.
41