80C186XL 80C188XL
(2a)
272431 – 3
272431 – 4
(2b)
Note 1
XTAL Frequency
L1 Value
20 MHz
12 0
mH
g
20%
25 MHz
8 2
mH
g
20%
32 MHz
4 7
mH
g
20%
40 MHz
3 0
mH
g
20%
LC network is only required when using a third
overtone crystal
Figure 2 Oscillator Configurations (see text)
INTRODUCTION
Unless specifically noted all references to the
80C186XL apply to the 80C188XL References to
pins that differ between the 80C186XL and the
80C188XL are given in parentheses
The following Functional Description describes the
base architecture of the 80C186XL The 80C186XL
is a very high integration 16-bit microprocessor It
combines 15 – 20 of the most common microproces-
sor system components onto one chip The
80C186XL is object code compatible with the
8086 8088 microprocessors and adds 10 new in-
struction types to the 8086 8088 instruction set
The 80C186XL has two major modes of operation
Compatible and Enhanced In Compatible Mode the
80C186XL is completely compatible with NMOS
80186 with the exception of 8087 support The En-
hanced mode adds three new features to the system
design These are Power-Save control Dynamic
RAM refresh and an asynchronous Numerics Co-
processor interface (80C186XL only)
The 80C186XL oscillator circuit is designed to be
used either with a parallel resonant fundamental or
third-overtone mode crystal depending upon the
frequency range of the application This is used as
the time base for the 80C186XL
The output of the oscillator is not directly available
outside the 80C186XL The recommended crystal
configuration is shown in Figure 2b When used in
third-overtone mode the tank circuit is recommend-
ed for stable operation Alternately the oscillator
may be driven from an external source as shown in
Figure 2a
The crystal or clock frequency chosen must be twice
the required processor operating frequency due to
the internal divide by two counter This counter is
used to drive all internal phase clocks and the exter-
nal CLKOUT signal CLKOUT is a 50% duty cycle
processor clock and can be used to drive other sys-
tem components All AC Timings are referenced to
CLKOUT
Intel recommends the following values for crystal se-
lection parameters
Temperature Range
Application Specific
ESR (Equivalent Series Resistance)
60X max
7 0 pF max
C
0
(Shunt Capacitance of Crystal)
C
1
(Load Capacitance)
Drive Level
20 pF
g
2 pF
2 mW max
80C186XL CORE ARCHITECTURE
80C186XL Clock Generator
The 80C186XL provides an on-chip clock generator
for both internal and external clock generation The
clock generator features a crystal oscillator a divide-
by-two counter synchronous and asynchronous
ready inputs and reset circuitry
4
4
INTEL [ INTEL CORPORATION ]
