MCP2510-SLASHST datasheet(49/80 Pages) MICROCHIP

49 / 80 page

DS21291F-page 49

MCP2510

8.0

OSCILLATOR

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

Oscillator Startup Timer

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,

RESET, or wake up from sleep mode occurs. It should

be noted that no SPI operations should be attempted

until after the OST has expired.

8.2

CLKOUT Pin

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 inter-

nal prescaler which can divide FOSC by 1, 2, 4 and 8.

The 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 (CAN-

CNTRL.CLKEN = ‘0’) the CLKOUT pin is in a high

impedance state.

The CLKOUT function is designed to guarantee that

thCLKOUT and tlCLKOUT timings are preserved when the

CLKOUT pin function is enabled, disabled, or the pres-

caler value is changed.

FIGURE 8-1:

CRYSTAL/CERAMIC RESONATOR OPERATION

FIGURE 8-2:

EXTERNAL CLOCK SOURCE

XTAL

OSC2

RS(1)

OSC1

RF(2)

SLEEP

To internal logic

Note 1:

A series resistor, RS, may be required for AT strip cut crystals.

Note 2:

The feedback resistor, RF , is typically in the range of 2 to 10 M

Ω.

Clock from

external system

OSC1

OSC2

Open

(1)

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).

MCP2510-/ST 数据表(PDF) 49 Page - Microchip Technology

MCP2510-/ST 数据表(HTML) 49 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80

数据表下载