5-3
CLOCK GENERATION AND POWER MANAGEMENT
Choose C
1
and L
1
component values in the third overtone crystal circuit to satisfy the following
conditions:
•
The LC components form an equivalent series resonant circuit at a frequency below the
fundamental frequency. This criterion makes the circuit inductive at the fundamental
frequency. The inductive circuit cannot make the 90° phase shift and oscillations do not
take place.
•
The LC components form an equivalent parallel resonant circuit at a frequency about
halfway between the fundamental frequency and the third overtone frequency. This
criterion makes the circuit capacitive at the third overtone frequency, necessary for oscil-
lation.
•
The two capacitors and inductor at X2, plus some stray capacitance, approximately equal
the 20 pF load capacitor, C
X2
, used alone in the fundamental mode circuit.
Figure 5-3. Crystal Connections to Microprocessor
Choosing C
1
as 200 pF (at least 10 times the value of the load capacitor) simplifies the circuit
analysis. At the series resonance, the capacitance connected to L
1
is 200 pF in series with 20 pF.
The equivalent capacitance is still about 20 pF and the equation in Figure 5-4(a) yields the series
resonant frequency.
X1
X2
(a)
Fundamental
Mode Circuit
X1
X2
(b)
Third Overtone
Mode Circuit
C
X2
C
X1
C
X2
C
X1
L
1
(c)
Third Overtone Mode
(Equivalent Circuit)
C
X2
L
1
C1
C
X1
= C
X2
C
1
L
1
= 20pF
= 200pF
= (See text)
A1520-0A
Содержание 80C186XL
Страница 1: ...80C186XL 80C188XL Microprocessor User s Manual...
Страница 2: ...80C186XL 80C188XL Microprocessor User s Manual 1995...
Страница 18: ...1 Introduction...
Страница 19: ......
Страница 27: ......
Страница 28: ...2 Overview of the 80C186 Family Architecture...
Страница 29: ......
Страница 79: ......
Страница 80: ...3 Bus Interface Unit...
Страница 81: ......
Страница 127: ......
Страница 128: ...4 Peripheral Control Block...
Страница 129: ......
Страница 137: ......
Страница 138: ...5 ClockGenerationand Power Management...
Страница 139: ......
Страница 154: ...6 Chip Select Unit...
Страница 155: ......
Страница 178: ...7 Refresh Control Unit...
Страница 179: ......
Страница 193: ......
Страница 194: ...8 Interrupt Control Unit...
Страница 195: ......
Страница 227: ......
Страница 228: ...9 Timer Counter Unit...
Страница 229: ......
Страница 253: ......
Страница 254: ...10 Direct Memory Access Unit...
Страница 255: ......
Страница 283: ......
Страница 284: ...11 Math Coprocessing...
Страница 285: ......
Страница 302: ...12 ONCE Mode...
Страница 303: ......
Страница 306: ...A 80C186 Instruction Set Additions and Extensions...
Страница 307: ......
Страница 318: ...B Input Synchronization...
Страница 319: ......
Страница 322: ...C Instruction Set Descriptions...
Страница 323: ......
Страница 371: ......
Страница 372: ...D Instruction Set Opcodes and Clock Cycles...
Страница 373: ......
Страница 396: ...Index...
Страница 397: ......