R8CSLASH15 datasheet(57/277 Pages) RENESAS

57 / 277 page

R8C/14 Group, R8C/15 Group

9. Clock Generation Circuit

Rev.2.10

Jan 19, 2006

Page 45 of 253

REJ09B0164-0210

The following describes the clocks generated by the clock generation circuit.

9.1

Main Clock

This clock is supplied by a main clock oscillation circuit. This clock is used as the clock source for the

CPU and peripheral function clocks. The main clock oscillation circuit is configured by connecting a

resonator between the XIN and XOUT pins. The main clock oscillation circuit contains a feedback

resistor, which is disconnected from the oscillation circuit in stop mode in order to reduce the amount of

power consumed in the chip. The main clock oscillation circuit may also be configured by feeding an

externally generated clock to the XIN pin. Figure 9.7 shows the Examples of Main Clock Connection

Circuit.

During reset and after reset, the main clock stops.

The main clock starts oscillating when the CM05 bit in the CM0 register is set to “0” (main clock on) after

setting the CM13 bit in the CM1 register to “1” (XIN- XOUT pin).

To use the main clock for the CPU clock source, set the OCD2 bit in the OCD register to “0” (select main

clock) after the main clock is oscillating stably.

The power consumption can be reduced by setting the CM05 bit in the CM0 register to “1” (stop main

clock) if the OCD2 bit is set to “1” (select on-chip oscillator clock).

When the clocks externally generated to the XIN pin are input, a main clock does not stop if setting the

CM05 bit to “1”. If necessary, use an external circuit to stop the clock.

In stop mode, all clocks including the main clock stop. Refer to 9.4 Power Control for details.

Figure 9.7

Examples of Main Clock Connection Circuit

XIN

XOUT

Microcomputer

(Built-In Feedback Resistor)

Rd(1)

COUT

CIN

XIN

XOUT

Microcomputer

(Built-In Feedback Resistor)

Externally Derived Clock

VCC

VSS

NOTES :

1. Insert a damping resistor if required. The resistance will vary depending on the oscillator and the oscillation drive

capacity setting. Use the value recommended by the maker of the oscillator.

When the oscillation drive capacity is set to low, check that oscillation is stable. Also, if the oscillator manufacturer's

data sheet specifies that a feedback resistor be added external to the chip, insert a feedback resistor between XIN

and XOUT following the instruction.

Open

Ceramic Resonator External Circuit

External Clock Input Clock

R8C/15 Datasheet(PDF) 57 Page - Renesas Technology Corp

R8C/15 Datasheet(HTML) 57 Page - Renesas Technology Corp

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL