Intel 80C188XL, 80C186XL user manual Clock Generation, Res, Crystal Oscillator

CHAPTER 5

CLOCK GENERATION AND POWER

MANAGEMENT

The clock generation and distribution circuits provide uniform clock signals for the Execution Unit, the Bus Interface Unit and all integrated peripherals. The 80C186 Modular Core Family processors have additional logic that controls the clock signals to provide power management functions.

5.1CLOCK GENERATION

The clock generation circuit (Figure 5-1) includes a crystal oscillator, a divide-by-two counter and power-save and reset circuitry. See “Power-Save Mode” on page 5-11 for a discussion of Power-Save mode as a power management option.

Schmitt Trigger

"Squares-up" CLKIN

X1

÷ 2	Clock
Clock	Divider

X2

Power Save

1 Internal

PhasePhase

Drivers

2 Clocks

To CLKOUT

Reset Circuitry

Internal Reset

RES

A1519-0A

Figure 5-1. Clock Generator

5.1.1Crystal Oscillator

The internal oscillator is a parallel resonant Pierce oscillator, a specific form of the common phase shift oscillator.

5-1