PIC16C765 Microchip Technology Inc., PIC16C765 Datasheet - Page 100

• Manufacturer Part Number: PIC16C765
• Description: 8-bit Cmos Microcontrollers With Usb
• Manufacturer: Microchip Technology Inc.

PIC16C745/765
13.2
13.2.1
The PIC16C745/765 can be operated in four different
oscillator modes. The user can program a configuration
bit (FOSC0) to select one of these four modes:
13.2.2
In HS mode, a crystal or ceramic resonator is con-
nected to the OSC1/CLKIN and OSC2/CLKOUT pins to
establish oscillation (Figure 13-1). The PIC16C745/
765 oscillator design requires the use of a parallel cut
crystal. Use of a series cut crystal may give a frequency
out of the crystal manufacturers specifications. When in
HS mode, the device can have an external clock
source to drive the OSC1/CLKIN pin (Figure 13-2). In
this mode, the oscillator start-up timer is active for a
period of 1024*T
MCU Reference Manual (DS33023) for details on
building an external oscillator.
FIGURE 13-1: CRYSTAL/CERAMIC
DS41124C-page 100
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•
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Note 1:
EC External Clock
E4 External Clock with internal PLL enabled
HS High Speed Crystal/Resonator
H4 High Speed Crystal/Resonator with
Oscillator Configurations
CRYSTAL OSCILLATOR/CERAMIC
RESONATORS
OSCILLATOR TYPES
C1
C2
internal PLL enabled
A series resistor may be required for AT strip cut
crystals.
Note1
OSC
XTAL
Rs
RESONATOR OPERATION
(HS OSC CONFIGURATION)
. See the PICmicro™ Mid-Range
OSC1
OSC2
Rf
PIC16C745/765
SLEEP
To internal
logic
Preliminary
TABLE 13-1:
TABLE 13-2:
13.2.3
In H4 mode, a PLL module is switched on in-line with
the clock provided across OSC1 and OCS2. The output
of the PLL drives F
13.2.4
An on-board 4x PLL provides a cheap means of gener-
ating a stable 24 MHz F
resonator. After power-up, a PLL settling time of less
than T
Ranges Tested:
These values are for design guidance only. See notes at
bottom of page.
HS
These values are for design guidance only. See notes at
bottom of page.
Note 1: Higher capacitance increases the stability
Osc Type
Mode
HS
2: Since each resonator/crystal has its own
3: Rs may be required in HS mode to avoid
4: When migrating from other PICmicro
5: Users should consult the USB Specification
PLLRT
H4 MODE
PLL
of the oscillator, but also increases the start-
up time.
characteristics, the user should consult the
resonator/crystal manufacturer for appropri-
ate values of external components.
overdriving crystals with low drive level
specification.
devices, oscillator performance should be
verified.
1.1 to ensure their resonator/crystal oscilla-
tor meets the required jitter limits for USB
operation.
is required.
6.0 MHz
6.0 MHz
Crystal
Freq
Freq
CERAMIC RESONATORS
CAPACITOR SELECTION FOR
CRYSTAL OSCILLATOR
INT
.
INT
2000 Microchip Technology Inc.
Cap. Range
, using an external 6 MHz
15 - 33 pF
10 - 68 pF
OSC1
C1
Cap. Range
15 - 33 pF
10 - 68 pF
OSC2
C2