Intel 80C186EA, User Manual

Page: 142 / 417

5-1
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.
5.1 CLOCK GENERATION
The clock generation circuit (Figure 5-1) includes a crystal oscillator, a divide-by-two counter,
power-save, powerdown, idle, and reset circuitry. See “Power Management” on page 5-10 for a
discussion of power management options.
Figure 5-1. Clock Generator
5.1.1 Crystal Oscillator
The internal oscillator is a parallel resonant Pierce oscillator, a specific form of the common
phase shift oscillator.
CLKIN
OSCOUT
RESIN
÷ 2
Clock
Clock
Divider
Phase
Drivers
Schmitt Trigger
"Squares-up" CLKIN
Reset Circuitry
Power Down
Idle
Power Save
Internal
Phase
Clocks
To CLKOUT
Internal Reset
1
2
A1118-0A