MCP2122
Infrared Encoder/Decoder
Features
• Pinout compatible with HSDL-7000
• Compliant with IrDA
®
Standard Physical Layer
Specification (version 1.3)
• UART to IrDA Standard Encoder/Decoder
- Interfaces with IrDA Standard Compliant
Transceiver
• Baud Rates:
- Up to IrDA Standard 115.2 Kbaud Operation
• Transmit/Receive Formats (Bit Width) Supported:
- 1.63 µs
• Low-power Mode (2 µA at 1.8V, +125°C)
• Pb-free packaging
Package Types
PDIP, SOIC
16XCLK
TX
RX
V
SS
1
2
3
4
8
7
6
5
V
DD
TXIR
RXIR
RESET
MCP2122
Block Diagram
MCP2122
TX
Encode
TXIR
CMOS Technology
• Low-voltage operation
• Extended temperature range
• Low power consumption
RESET
Reset
Logic
Baud Rate
Generator
Decode
RXIR
16XCLK
RX
IrDA Family Selection
Baud Rate
Device
Host
UART
IR
Encoder
/
Decoder
Yes
Yes
Yes
Yes
Yes
Protocol
Layer
Handler
No
No
IrCOMM
(3)
IrCOMM
(3)
IrCOMM
(3)
Clock
Source
XTAL
16XCLK
XTAL
XTAL
XTAL
Host UART
Baud Rate
Selection
HW/SW
By 16XCLK
None - Fixed
HW
HW
Host UART easily interfaces to
a PC’s serial port (DTE)
Host UART easily interfaces to
a modem’s serial port (DCE)
Extended Temperature Range
(-40°C to +125°C)
Comment
MCP2120
2400 -
2400 -
(1)
312,500
312,500
(1)
MCP2122
2400 -
2400 -
(1)
115,200
115,200
(1)
MCP2140
9600
9600
MCP2150
9600 -
9600 -
115,200
(2)
115,200
(2)
MCP2155
9600 -
9600 -
(2)
115,200
(2)
115,200
Note 1:
The host UART and the IR operate at the same baud rates.
2:
The host UART and IR baud rates operate independent of each other.
3:
Supports the 9-wire “cooked” service class of the IrCOMM Application Layer Protocol.
©
2007 Microchip Technology Inc.
Preliminary
DS21894C-page 1
MCP2122
NOTES:
DS21894C-page 2
Preliminary
©
2007 Microchip Technology Inc.
MCP2122
1.0
DEVICE OVERVIEW
TABLE 1-1:
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 4300) or it could be implemented with
discrete components. For additional information, please
refer to AN243, “Fundamentals of the Infrared Physical
Layer” (DS00243).
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.
MCP2122 FEATURES
OVERVIEW
MCP2122
UART, IR
16XCLK
Yes
8-pin PDIP
8-pin SOIC
Features
Serial Communications:
Baud Rate Selection:
Low-power Mode:
Packages:
Infrared Technology Features:
• Universal standard for connecting portable
computing devices
• Effortless implementation
• Economical alternative to other connectivity
solutions
• 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
each other
• Enhances mobility by allowing users to easily
connect
1.1
Applications
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
FIGURE 1-1:
SYSTEM BLOCK DIAGRAM
Host Controller
PIC
®
MCU
Host UART
Interface
Protocol Handler
MCP2122
TX
Encode
TXIR
IR
Optical
Interface Transceiver
TFDU 4300
TXD
SO
UART
SI
RESET
Clock
(I/O)
16XCLK
RX
Decode
Reset
Logic
Clock
Logic
RXIR
RXD
©
2007 Microchip Technology Inc.
Preliminary
DS21894C-page 3
MCP2122
TABLE 1-2:
Pin Name
16XCLK
TX
RX
V
SS
RESET
PIN DESCRIPTION
Pin Number
PDIP
1
2
3
4
5
SOIC
1
2
3
4
5
Pin
Type
I
I
O
—
I
Buffer
Type
ST
ST
—
P
ST
Description
16x external clock source input
Asynchronous receive from Host Controller UART
Asynchronous transmit to Host Controller UART
Ground reference for logic and I/O pins
Resets the Device
H = Normal Operation
L = Device in Reset
Asynchronous receive from infrared transceiver
Asynchronous transmit to infrared transceiver
Positive supply for logic and I/O pins
RXIR
TXIR
V
DD
Legend:
ST
I
P
O
6
7
8
=
=
=
=
6
7
8
I
O
—
ST
—
P
Schmitt Trigger input with CMOS levels
Input
Power
Output
DS21894C-page 4
Preliminary
©
2007 Microchip Technology Inc.
MCP2122
2.0
DEVICE OPERATION
TABLE 2-1:
Input Pin
Name
RESET
State
L
The MCP2122 is a low-cost infrared encoder/decoder.
The baud rate is the same for the host UART and IR
interfaces and is determined by the frequency of the
16XCLK signal, with a maximum baud rate of
115.2 Kbaud.
The MCP2122 is made up of these functional modules:
• Clock Driver (16XCLK)
• Reset
• IR Encoder/Decoder
- IrDA Standard Encoder
- IrDA Standard Decoder
The
16XCLK
circuit allows a clock input to provide the
device clock.
The
Reset
circuit supports an external reset signal.
The
IR Encoder
logic takes a data bit and converts it to
the IrDA standard signal according to the IrDA standard
Physical Layer specification, while the
IR Decoder
logic takes the IrDA standard signal and converts it to
8-bit data bytes.
DEFAULT OUTPUT PIN
STATES IN DEVICE RESET
Output Pin
State
RX
H
TXIR
L
Device in Reset mode
Comments
TABLE 2-2:
DEFAULT OUTPUT PIN
STATES AFTER DEVICE
RESET (RESET = L→H)
Output Pin
State
RX
—
TXIR
L→H After 7 - 8 16XCLK
→L
pulses, the TXIR pin
will pulse high.
L
—
—
After 4 16XCLK pulses,
RX = L.
Comments
Input Pin
Name State
TX
L
H
RXIR
L
H
—
H→L
H
2.1
Power-up
As the device is powered up, there will be a voltage
range in which the device will not operate properly. The
device should be reset once it has entered the normal
operating range (from an out-of-voltage condition). The
RESET pin may then be forced high.
Other device operating parameters (such as frequency,
temperature, etc.) must also be within their operating
ranges when the device exits reset. Otherwise, the
device may not function as desired.
2.3
Decoupling
2.2
Device Reset
It is highly recommended that the MCP2122 have a
decoupling capacitor (C
BYP
). A 0.01 µF capacitor is
recommended as a starting value, but an evaluation of
the best value for your circuit/layout should be
performed. Place this decoupling capacitor (C
BYP
) as
close to the MCP2122 as possible (see
Figure 2-1).
The MCP2122 is forced into the known state (RESET)
when the RESET pin is in the low state. Once the
RESET pin is brought to a high state, the device begins
normal operation (if the device operating parameters
are met).
Table 2-1
shows the states of the output pins
while the device is in reset (RESET = Low).
Table 2-2
shows the state of the output pins once the device exits
reset, RESET = L→H (device in Normal Operation
mode).
The MCP2122 has a RESET noise filter in the RESET
input signal path. The filter will detect and ignore small
pulses.
Using the RESET pin to enter a low-power state is
discussed in
Section 2.9 “Minimizing Power”.
FIGURE 2-1:
V
DD
DEVICE DECOUPLING
MCP2122
V
DD
V
SS
RESET
16XCLK
TX
RX
C
BYP
(bypass
capacitor)
TXIR
RXIR
©
2007 Microchip Technology Inc.
Preliminary
DS21894C-page 5
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