1.0 DEVICE OVERVIEW
The MCP2122 is a stand-alone IrDA standard encoder/
decoder device that is pinout-compatible with the
Agilent® HSDL-7000 encoder/decoder.
The MCP2122 has two interfaces: the host UART
interface and the IR interface (see Figure 1-1). The host
UART interfaces to the UART of the Host Controller.
The Host Controller is the device in the embedded
system that transmits and receives the data. The IR
interface connects to an infrared (IR) optical transceiver
circuit that converts electrical pulses into IR light
(encode) and converts IR light into electrical pulses
(decode). This IR optical transceiver circuit could be
either a standard infrared optical transceiver (such as a
Vishay® TFDU 4100) or it could be implemented with
discrete components. For additional information, please
refer to AN243, “Fundamentals of the Infrared Physical
When the Host Controller transmits the UART format
data, the MCP2122 receives this UART data and
encodes (modulates) it bit by bit. This encoded data is
then output as electrical pulses to the IR transceiver.
The IR transceiver will then convert these electrical
pulses to IR light pulses.
The IR transceiver also receives IR light pulses (data),
which are outputted as electrical pulses. The MCP2122
decodes (demodulates) these electrical pulses, with
the data then being transmitted by the MCP2122
UART. This modulation/demodulation method is
performed in accordance with the IrDA standard.
Table 1-1 shows an overview of some of the device
features. Figure 1-1 shows a typical application block
diagram. Table 1-2 shows the pin definitions of the
MCP2122 during normal operation.
Baud Rate Selection:
Infrared Technology Features:
• Universal standard for connecting portable
• Effortless implementation
• Economical alternative to other connectivity
• Reliable, high-speed connection
• Safe to use in any environment; can even be used
during air travel
• Eliminates the hassle of cables
• Allows PCs and non-PCs to communicate with
• Enhances mobility by allowing users to easily
Some applications where an IR interface (MCP2122)
could be used include:
• Data-Logging/Data Exchange
• System Setup
• System Diagnostic Read Out
• Manufacturing Configuration
• Host Controller Firmware Updates
• System Control
SYSTEM BLOCK DIAGRAM
2004 Microchip Technology Inc.