MCP2510 Microchip Technology, MCP2510 Datasheet - Page 49

• Manufacturer Part Number: MCP2510
• Description: Stand-Alone CAN Controller with SPI Interface
• Manufacturer: Microchip Technology

8.0
The MCP2510 is designed to be operated with a crystal
or ceramic resonator connected to the OSC1 and
OSC2 pins. The MCP2510 oscillator design requires
the use of a parallel cut crystal. Use of a series cut crys-
tal may give a frequency out of the crystal manufactur-
ers specifications. A typical oscillator circuit is shown in
Figure 8-1. The MCP2510 may also be driven by an
external clock source connected to the OSC1 pin as
shown in Figure 8-2 and Figure 8-3.
8.1
The MCP2510 utilizes an oscillator startup timer
(OST), which holds the MCP2510 in reset, to insure
that the oscillator has stabilized before the internal
state machine begins to operate. The OST maintains
reset for the first 128 OSC1 clock cycles after power up
or wake up from sleep mode occurs. It should be noted
that no SPI operations should be attempted until after
the OST has expired.
FIGURE 8-1: Crystal/Ceramic Resonator Operation
FIGURE 8-2: External Clock Source
1999 Microchip Technology Inc.
Note 1: A series resistor,
Note 2: The feedback resistor,
Note 1: A resistor to ground may be used to reduce system noise. This may increase system current.
Note 2: Duty cycle restrictions must be observed (see Table 12-2).
OSCILLATOR
Oscillator Startup Timer
external system
clock from
R
S
C1
C2
, may be required for AT strip cut crystals.
R
F
, is typically in the range of 2 to 10 M
R
XTAL
S
OSC1
OSC2
(1)
Open
(1)
Preliminary
R
F
(2)
8.2
The clock out pin is provided to the system designer for
use as the main system clock or as a clock input for other
devices in the system. The CLKOUT has an internal
prescaler which can divide F
CLKOUT function is enabled and the prescaler is
selected via the CANCNTRL register (see Register 9-1).
The CLKOUT pin will be active upon system reset and
default to the slowest speed (divide by 8) so that it can be
used as the MCU clock. When sleep mode is requested,
the MCP2510 will drive sixteen additional clock cycles on
the CLKOUT pin before entering sleep mode. The idle
state of the CLKOUT pin in sleep mode is low. When the
CLKOUT function is disabled (CANCNTRL.CLKEN = ‘0’)
the CLKOUT pin is in a high impedance state.
The CLKOUT function is designed to guarantee that
t
CLKOUT pin function is enabled, disabled, or the pres-
caler value is changed.
hCLKOUT
SLEEP
To internal logic
OSC1
OSC2
CLKOUT Pin
and t
lCLKOUT
timings are preserved when the
OSC
MCP2510
by 1, 2, 4 and 8. The
DS21291C-page 49