MCP2140 データシートの表示（PDF） - Microchip Technology

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MCP2140

IrDA® Standard Protocol Stack Controller With Fixed 9600 Baud Communication Rate

Microchip Technology 

2.0 DEVICE OPERATION

The MCP2140 serial interface and IR baud rates are

fixed at 9600 baud, given a 7.3728 MHz device clock.

2.1 Power-Up

Any time the device is powered up (Parameter D003),

the Power-Up Timer delay (Parameter 33) occurs, fol-

lowed by an Oscillator Start-up Timer (OST) delay

(Parameter 32). Once these delays complete, commu-

nication with the device may be initiated. This commu-

nication is from both the infrared transceiver’s side and

the controller’s UART interface.

2.2 Device Reset

The MCP2140 is forced into the reset state when the

RESET pin is in the low state. Once the RESET pin is

brought to a high state, the Device Reset sequence

occurs. Once the sequence completes, functional

operation begins.

2.3 Device Clocks

The MCP2140 requires a clock source to operate. This

clock source is used to establish the device timing,

including the device “Bit Clock”.

2.3.1 CLOCK SOURCE

The clock source can be supplied by one of the

following:

• Crystal

• Resonator

• External clock

The frequency of this clock source must be

7.3728 MHz (electrical specification Parameter 1A) for

device communication at 9600 baud.

MCP2140

2.3.1.1

Crystal Oscillator / Ceramic

Resonators

A crystal or ceramic resonator can be connected to the

OSC1 and OSC2 pins to establish oscillation

(Figure 2-1). The MCP2140 oscillator design requires

the use of a parallel-cut crystal. Use of a series of cut

crystals may give a frequency outside of the crystal

manufacturers specifications.

FIGURE 2-1:

C1

CRYSTAL OPERATION

(CERAMIC RESONATOR)

OSC1

To internal

logic

XTAL

OSC2

RS

C2 (Note)

RF

MCP2140

See Table 2-1 and Table 2-2 for recommended

values of C1 and C2.

Note: A series resistor may be required for

AT strip cut crystals.

TABLE 2-1: CAPACITOR SELECTION FOR

CERAMIC RESONATORS

Freq

OSC1 (C1) OSC2 (C2)

7.3728 MHz

10 - 22 pF

10 - 22 pF

Note:

Higher capacitance increases the stability

of the oscillator, but also increases the

start-up time. These values are for design

guidance only. Since each resonator has its

own characteristics, the user should consult

the resonator manufacturer for appropriate

values of external components.

TABLE 2-2:

Freq

CAPACITOR SELECTION FOR

CRYSTAL OSCILLATOR

OSC1 (C1)

OSC2 (C2)

7.3728 MHz

15 - 30 pF

15 - 30 pF

Note:

Higher capacitance increases the stability

of the oscillator but also increases the start-

up time. These values are for design guid-

ance only. RS may be required to avoid

overdriving crystals with low drive level

specification. Since each crystal has its

own characteristics, the user should con-

sult the crystal manufacturer for

appropriate values of external components.

 2003 Microchip Technology Inc.

Preliminary

DS21790A-page 7

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