MCP2140AT-ISLASHSS datasheet(47/60 Pages) MICROCHIP

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DS22050A-page 47

MCP2140A

APPENDIX A:

REVISION HISTORY

Revision A (June 2007)

• Original release of this document

APPENDIX B:

HOW DEVICES

CONNECT

When two devices implementing the IrDA standard

feature establish a connection using the IrCOMM

protocol, the process is analogous to connecting two

devices with serial ports using a cable. This is referred

to as a “point-to-point” connection. This connection is

limited to half-duplex operation because the IR

transceiver cannot transmit and receive at the same

time. The purpose of the IrDA protocols is to allow this

half-duplex link to emulate, as much as possible, a full-

duplex connection. In general, this is done by dividing

the data into “packets”, or groups of data. These

packets can then be sent back and forth, when needed,

without risk of collision. The rules of how and when

these packets are sent constitute the IrDA protocol.

The MCP2140A supports elements of this IrDA

standard protocol to communicate with other IrDA

standard compatible devices.

When a wired connection is used, the assumption is

made that both sides have the same communications

parameters and features. A wired connection has no

need to identify the other connector because it is

assumed that the connectors are properly connected.

In the IrDA standard, a connection process has been

defined to identify other IrDA compatible devices and

establish a communication link. There are three steps

that these two devices go through to make this

connection. They are:

• Normal Disconnect Mode (NDM)

• Discovery Mode

• Normal Connect Mode (NCM)

Figure B-1 shows the connection sequence.

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