SX18AA100-I/DP ETC [List of Unclassifed Manufacturers], SX18AA100-I/DP Datasheet - Page 21

• Manufacturer Part Number: SX18AA100-I/DP
• Description: Configurable Communications Controllers with EE/Flash Program Memory, In-System Programming Capability and On-Chip Debug
• Manufacturer: ETC [List of Unclassifed Manufacturers]

9.0 OSCILLATOR CIRCUITS
The device supports several user-selectable oscillator
modes. The oscillator modes are selected by program-
ming the appropriate values into the FUSE Word register.
These are the different oscillator modes offered:
9.1 XT, LP or HS modes
In XT, LP or HS, modes, you can use either an external
resonator network or an external clock signal as the
device clock.
To use an external resonator network, you connect a
crystal or ceramic resonator to the OSC1/CLKIN and
OSC2/CLKOUT pins according to the circuit configura-
tion shown in Figure 9-1. A parallel resonant crystal type
is recommended. Use of a series resonant crystal may
result in a frequency that is outside the crystal manufac-
turer specifications. Table 9-1 shows the recommended
external components associated with a crystal-based
oscillator. Table 9-2 shows the recommended external
component values for a resonator-based oscillator.
Bits 0, 1 and 5 of the FUSE register (FOSC1:FOSC2) are
used to configure the different external resonator/crystal
oscillator modes. These bits allow the selection of the
appropriate gain setting for the internal driver to match
the desired operating frequency. If the XT, LP, or HS
mode is selected, the OSC1/CLKIN pin can be driven by
an external clock source rather than a resonator network,
as long as the clock signal meets the specified duty
cycle, rise and fall times, and input levels (Figure 9-2). In
this case, the OSC2/CLKOUT pin should be left open.
© 2000 Scenix Semiconductor, Inc. All rights reserved.
LP: Low Power Crystal
XT: Crystal/Resonator
HS: High Speed Crystal/Resonator
RC: External Resistor/Capacitor
Internal Resistor/Capacitor
FOSC2:FOSC0
Table 9-1. External Component Selection for Crystal Oscillator(Vdd=5.0V)
010
011
011
011
100
* 50 MHz fundamental crystal
Frequency
50* MHz
Crystal
20 MHz
32 MHz
4 MHz
8 MHz
- 21 -
15 pF
56 pF
33 pF
15 pF
15 pF
C1
Figure 9-1. Crystal Operation (or Ceramic Resonator)
SX18AC/SX20AC/SX28AC/SX18AC75/SX20AC75/SX28AC75
Figure 9-2. External Clock Input Operation
22 pF
33 pF
22 pF
22 pF
15 pF
(HS, XT or LP OSC Configuration)
(HS, XT or LP OSC Configuration)
C2
OSC1
Generated Clock
C
1
OSC1
Externally
R
M
M
M
M
M
SX Device
SLEEP
SX Device
F
XTAL
RF
Internal
Circuitry
Open
OSC2
0
0
0
0
0
R
S
OSC2
RS
C
2
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