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Chapter 5 / The Electronics
printers and modem devices. The IrCOMM standard is just a syntax
that allows the primary device to consider the secondary device as a
serial device. IrCOMM allows for emulation of serial or parallel (print-
er) connections of various capabilities.
The MCP2150 (PDA Robot) supports the 9-wire “cooked” service class
of IrCOMM. Other service classes supported by IrCOMM are shown in
Figure 5.27. Note: The MCP2150 identifies itself as a modem to ensure
that it is identified as a serial device with a limited amount of memory.

Figure 5.27
Services supported by IrCOMM.

PDA and PDA Robot Handshake:
How Devices Connect

When two devices implementing the IrDA standard feature (PDA and
PDA Robot) 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 con-
nection is limited to half-duplex operation because the IR transceiver
cannot transmit and receive at the same time. The purpose of the IrDA
protocol is to allow this half-duplex link to emulate, as much as pos-
sible, 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 protocols.
The MCP2150 supports elements of this IrDA protocol to communi-
cate with other IrDA standard compatible devices. When a wired con-

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