MICROCHIP MCP2150 Technical data

IrDA® Standard Protocol Stack Controller

MCP2150

Supporting DTE Applications

Features

• Implements the IrDA® standard including:

-IrLAP

-IrLMP

-IAS

-TinyTP

- IrCOMM (9-wire “cooked” service class)

• Provides IrDA standard physical signal layer support including:

- Bidirectional communication

- CRC implementation

- Data communication rates up to 115.2 kbaud

• Includes UART to IrDA standard encoder/decoder functionality:

- Easily interfaces with industry standard

UARTs and infrared transceivers

• UART interface for connecting to Data Terminal Equipment (DTE) systems

• Transmit/Receive formats (bit width) supported:

-1.63µs

• Hardware baud rate selection for UART:

- 9.6 kbaud

- 19.2 kbaud

- 57.6 kbaud

- 115.2 kbaud

• Infrared baud rates supported:

- 9.6 kbaud

- 19.2 kbaud

- 38.4 kbaud

- 57.6 kbaud

- 115.2 kbaud

• 64 Byte Data Packet Size

• Programmable Device ID String

• Operates as Secondary Device

CMOS Technology

• Low power, high-speed CMOS technology

• Fully static design

• Low voltage operation

• Industrial temperature range

• Low power consumption

- < 1 mA @ 3.3 V, 11.0592 MHz (typical)

- 3 µA typical @ 5.0 V when disabled

Package Types

PDIP, SOIC

1 2 3 4 5

7 8 9

1 2 3 4 5 6 7 8 9 10

17 16

MCP2150

15 14 13 12 11 10

20 19 18

MCP2150

17 16 15 14 13 12

SSOP

BAUD0

TXIR

RXIR

RESET

BAUD0

TXIR

RXIR

RESET

RI DSR

Block Diagram

MCP2150

TX TXIR

BAUD1 BAUD0

RTS

CTS DSR DTR

Encode and

Protocol Handler

Logic

Baud Rate

Generator

Protocol Handler

and Decode

UART

Control

BAUD1 CD OSC1/CLKI OSC2

V RTS CTS DTR DSR

BAUD1 CD OSC1/CLKI OSC2

V RTS CTS DTR

RXIR

OSC1 OSC2

 2002 Microchip Technology Inc. Preliminary

DS21655B-page 1

MCP2150

NOTES:

DS21655B-page 2

Preliminary  2002 Microchip Technology Inc.

MCP2150

1.0 DEVICE OVERVIEW

This document contains device specific information for the following device:

• MCP2150

The MCP2150 is a cost effective, low pin count (18-pin), easy to use device for implementing IrDA standard wireless connectivity. The MCP2150 provides support for the IrDA standard protocol “stack” plus bit encoding/ decoding.

The serial interface baud rates are user selectable to one of four IrDA standard baud rates between 9600 baud and 115.2 kbaud (9600, 19200, 57600, 115200). The IR baud rates are user selectable to one of five IrDA standard baud rates between 9600 baud and

115.2 kbaud (9600, 19200, 37400, 57600, 115200). The serial interface baud rate will be specified by the BAUD1:BAUD0 pins, while the IR baud rate is specified by the Primary Device (during Discover phase). This means that the baud rates do not need to be the same. The MCP2150 operates in Data Terminal Equipment (DTE) applications and sits between a UART and an infrared optical transceiver.

The MCP2150 encodes an asynchronous serial data stream, converting each data bit to the corresponding infrared (IR) formatted pulse. IR pulses received are decoded and then handled by the protocol handler state machine. The protocol handler sends the appropriate data bytes to the Host Controller in UART formatted serial data.

The MCP2150 supports “point-to-point” applications. That is, one Primary device and one Secondary device. The MCP2150 operates as a Secondary device. It does not support “multi-point” applications.

Sending data using IR light requires some hardware and the use of specialized communication protocols. These protocol and hardware requirements are described, in detail, by the IrDA standard specifications. The encoding/decoding functionality of the MCP2150 is designed to be compatible with the physical layer component of the IrDA standard. This part of the standard is often referred to as “IrPHY”.

The complete IrDA standard specifications are available for download from the IrDA website (www.IrDA.org).

 2002 Microchip Technology Inc. Preliminary

DS21655B-page 3

MCP2150

1.1 Applications

The MCP2150 Infrared Communications Controller supporting the IrDA standard provides embedded system designers the easiest way to implement IrDA standard wireless connectivity. Figure 1-1 shows a typical application block diagram. Table 1-2 shows the pin definitions.

TABLE 1-1: OVERVIEW OF FEATURES

Features MCP2150

Serial Communications UART, IR

Baud Rate Selection Hardware

Low Power Mode Yes

Resets (and Delays) RESET

Packages 18-pin DIP, SOIC,

, POR

(PWRT and OST)

20-pin SSOP

Infrared communication is a wireless two-way data connection, using infrared light generated by low-cost transceiver signaling technology. This provides reliable communication between two devices.

Infrared technology offers:

• Universal standard for connecting portable computing devices

• Easy, 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 other electronic devices (such as PDAs, cell phones, etc.) to communicate with each other

• Enhances mobility by allowing users to easily connect

The MCP2150 allows the easy addition of IrDA standard wireless connectivity to any embedded application that uses serial data. Figure 1-1 shows typical implementation of the MCP2150 in an embedded system.

The IrDA protocols for printer support are not included in the IrCOMM 9-wire “cooked” service class.

FIGURE 1-1: SYSTEM BLOCK DIAGRAM

Host Controller

(Microcontroller)

UART

BAUD1 BAUD0

RTS

CTS DSR DTR

MCP2150

Encode

Power Down

Logic

Decode

Baud Rate

Generator

UART

Control

TXIR

RXIR

Optical

Transceiver

TXD

RXD

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Preliminary  2002 Microchip Technology Inc.

TABLE 1-2: PIN DESCRIPTIONS

MCP2150

Pin Name

BAUD0 1 1 1 I ST BAUD1:BAUD0 specify the baud rate of the device.

TXIR 2 2 2 O — Asynchronous transmit to Infrared transceiver.

RXIR 3 3 3 I ST Asynchronous receive from Infrared transceiver.

4 4 4 I ST Resets the device.

RESET

SS 5 5 5, 6 — P Ground reference for logic and I/O pins.

EN 6 6 7 I TTL Device enable.

TX 7 7 8 I TTL Asynchronous receive; from Host Controller UART.

RX 8 8 9 O — Asynchronous transmit; to Host Controller UART.

RI 9 9 10 — — Ring Indicator. The value on this pin is driven high.

DSR 10 10 11 O — Data Set Ready. Indicates that the MCP2150 has completed

DTR 11 11 12 I TTL Data Terminal Ready. The value of this pin is ignored once

CTS 12 12 13 O — Clear to Send. Indicates that the MCP2150 is ready to

RTS 13 13 14 I TTL Request to Send. Indicates that a Host Controller is ready to

14 14 15, 16 — P Positive supply for logic and I/O pins.

OSC2 15 15 17 O — Oscillator crystal output.

OSC1/CLKIN 16 16 18 I CMOS Oscillator crystal input/external clock source input.

CD 17 17 19 O — Carrier Detect. Indicates that the MCP2150 has established a

BAUD1 18 18 20 I ST BAUD1:BAUD0 specify the baud rate of the device.

Legend: TTL = TTL compatible input

I = Input P = Power

Pin Number

PDIP SOIC SSOP

Buffer

Type

1 = Device is enabled. 0 = Device is disabled (low power). MCP2150 only monitors

this pin when in the NDM state.

reset.

1 = MCP2150 is initialized. 0 = MCP2150 is not initialized.

the MCP2150 is initialized. It is recommended that this pin be connected so that the voltage level is either V device power up, this signal is used with the RTS signal to enter device ID programming.

1 = Enter Device ID programming mode (if RTS is cleared). 0 = Do not enter Device ID programming mode.

receive data from the Host Controller.

1 = Host Controller should not send data. 0 = Host Controller may send data.

receive data from the MCP2150. The MCP2150 prepares to send data, if available.

1 = Host Controller not ready to receive data. 0 = Host Controller ready to receive data.

At device power up, this signal is used with the DTR signal to enter device ID programming.

1 = Do not enter Device ID programming mode. 0 = Enter Device ID programming mode (if DTR is set).

valid link with a Primary Device.

1 = An IR link has not been established (No IR Link). 0 = An IR link has been established (IR Link).

ST = Schmitt Trigger input with CMOS levels O = Output CMOS = CMOS compatible input

Description

SS or VCC. At

 2002 Microchip Technology Inc. Preliminary

DS21655B-page 5

MCP2150

1.1.1 SIGNAL DIRECTIONS

Table 1-3 shows the direction of the MCP2150 signals.

The MCP2150 is designed for use in Data Terminal Equipment (DTE) applications.

TABLE 1-3: MCP2150 S IGNAL DIRECTION

DB-9

Pin No.

Legend: HC = Host Controller

Note 1: This signal is not implemented in the MCP2150.

Signal Direction Comment

1 CD MCP2150 → HC Carrier Detect 2 RX MCP2150 → HC Received Data 3 TX HC → MCP2150 Transmit Data

4DTR

5 GND — Ground 6 DSR MCP2150 → HC Data Set Ready 7 RTS HC → MCP2150 R equest to Send 8 CTS MCP2150 → HC Clear to Send

9RI

(1)

— Ring Indicator

— Data Terminal

Ready

DS21655B-page 6

Preliminary  2002 Microchip Technology Inc.

MCP2150

2.0 DEVICE OPERATION

The MCP2150 is a cost effective, low pin count (18pin), easy to use device for implementing IrDA standard wireless connectivity. The MCP2150 provides support for the IrDA standard protocol “stack” plus bit encoding/decoding. The Serial interface and IR baud rates are independantly selectable.

2.1 Power Up

Any time the device is powered up (parameter D003), the Power Up Timer delay (parameter 33) occurs, followed by an Oscillator Start-up Timer (OST) delay (parameter 32). Once these delays complete, communication with the device may be initiated. This communication is from both the infrared transceiver’s side as well as the controller’s UART interface.

2.2 Device Reset

The MCP2150 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 Clock Source

The MCP2150 requires a clock source to operate. The frequency of this clock is 11.0592 MHz (electrical specification parameter 1A). This clock can be supplied by either a crystal/resonator or as an external clock input.

2.3.1 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 MCP2150 oscillator design requires the use of a parallel cut crystal. Use of a series cut crystal may give a frequency outside of the crystal manufacturers specifications.

FIGURE 2-1: CRYSTAL OPERATION

(OR CERAMIC RESONATOR)

TABLE 2-1: CAPACITOR SELECTION FOR

CERAMIC RESONATORS

Freq OSC1 (C1) OSC2 (C2)

11.0592 MHz 10 - 22 pF 10 - 22 pF

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: CAPACITOR SELECTION FOR

CRYSTAL OSCILLATOR

Freq OSC1 (C1) OSC2 (C2)

11.0592 MHz 15 - 30 pF 15 - 30 pF

Higher capacitance increases the stability of the oscillator but also increases the start-up time. These values are for design guidance only. R to avoid overdriving crystals with low drive level specification. Since each crystal has its own characteristics, the user should consult the crystal manufacturer for appropriate values of external components.

S may be required

2.3.2 EXTERNAL CLOCK IN

For applications where a clock is already available elsewhere, users may directly drive the MCP2150 provided that this external clock source meets the AC/DC timing requirements listed in Section 4.3. Figure 2-2 shows how an external clock circuit should be configured.

FIGURE 2-2: EXTERNAL CLOCK INPUT

OPERATION

Clock From external system

Open

OSC1

MCP2150

OSC2

OSC1

XTAL

OSC2

Note

See Tab le 2 -1 and Tab le 2- 2 for recommended values of C1 and C2.

Note: A series resistor may be required for AT

strip cut crystals.

 2002 Microchip Technology Inc. Preliminary

To internal logic

MCP2150

DS21655B-page 7

MCP2150

2.4 Bit Clock

The device crystal is used to derive the communication bit clock (BITCLK). There are 16 BITCLKs for each bit time. The BITCLKs are used for the generation of the start bit and the eight data bits. The stop bit uses the BITCLK when the data is transmitted (not for reception).

This clock is a fixed frequency and has minimal variation in frequency (specified by crystal manufacturer).

2.5 UART Interface

The UART interface communicates with the "controller". This interface is a half duplex interface, meaning that the system is either transmitting or receiving, but not both simultaneously.

2.5.1 BAUD RATE

The baud rate for the MCP2150 serial port (the TX and RX pins) is configured by the state of the BAUD1 and BAUD0 pins. These two device pins are used to select the baud rate at which the MCP2150 will transmit and receive serial data (not IR data). Table 2-3 shows the baud rate configurations.

TABLE 2-3: SERIAL BAUD RATE

SELECTION VS. FREQUENCY

BAUD1:BAUD0

00 9600 F 01 19200 F 10 57600 F 11 115200 F

Baud Rate @

11.0592 MHz

Bit Rate

OSC / 1152

OSC / 576

OSC / 192

OSC / 96

2.5.2 TRANSMITTING

When the controller sends serial data to the MCP2150, the controller’s baud rate is required to match the baud rate of the MCP2150’s serial port.

2.5.3 RECEIVING

When the controller receives serial data from the MCP2150, the controller’s baud rate is required to match the baud rate of the MCP2150’s serial port.

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Preliminary  2002 Microchip Technology Inc.

MCP2150

2.6 Modulation

The data that the MCP2150 UART received (on the TX pin) that needs to be transmitted (on the TXIR pin) will need to be modulated. This modulated signal drives the IR transceiver module. Figure 2-3 shows the encoding of the modulated signal.

Note: The signal on the TXIR pin does not actu-

ally line up in time with the bit value that was transmitted on the TX pin, as shown in

Figure 2-3. The TX bit value is shown to

represent the value to be transmitted on the TXIR pin.

Each bit time is comprised of 16-bit clocks. If the value to be transmitted (as determined by the TX pin) is a logic low, then the TXIR pin will output a low level for 7-bit clock cycles, a logic high level for 3-bit clock cycles or a minimum of 1.6 µsec. (see parameter

IR121). The remaining 6-bit clock cycles will be low. If

the value to transmit is a logic high, then the TXIR pin will output a low level for the entire 16-bit clock cycles.

FIGURE 2-3: ENCODING

2.7 Demodulation

The modulated signal (data) from the IR transceiver module (on RXIR pin) needs to be demodulated to form the received data (on RX pin). Once demodulation of the data byte occurs, the data that is received is transmitted by the MCP2150 UART (on the RX pin).

Figure 2-4 shows the decoding of the modulated

signal.

Note: The signal on the RX pin does not actually

line up in time with the bit value that was received on the RXIR pin, as shown in

Figure 2-4. The RXIR bit value is shown to

represent the value to be transmitted on the RX pin.

Each bit time is comprised of 16-bit clocks. If the value to be received is a logic low, then the RXIR pin will be a low level for the first 3-bit clock cycles or a minimum of 1.6 µs. The remaining 13-bit clock cycles (or difference up to the 16-bit clock time) will be high. If the value to be received is a logic high, then the RXIR pin will be a high level for the entire 16-bit clock cycles. The level on the RX pin will be in the appropriate state for the entire 16 clock cycles.

Start Bit Data bit 0 Data bit 1 Data bit 2 Data bit ...

16 CLK

BITCLK

TX Bit Value

TXIR

7 CLK

24 Tosc

0100 01

FIGURE 2-4: DECODING

Start Bit Data bit 0 Data bit 1 Data bit 2 Data bit ...

16 CLK

BITCLK (CLK)

RXIR Bit Valu e

≥ 1.6 µs (up to 3 CLK)

16 CLK 16 CLK 16 CLK 16 CLK 16 CLK 16 CLK

≥ 13 CLK

0100 01

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DS21655B-page 9

MCP2150

2.8 Minimizing Power

The device can be placed in a low power mode by disabling the device (holding the EN pin at the low state). The internal state machine is monitoring this pin for a low level and, once this is detected, the device is disabled and enters into a low power state.

2.8.1 RETURNING TO DEVICE OPERATION

When disabled, the device is in a low power state. When the EN pin is brought to a high level, the device will return to the operating mode. The device requires a delay of 1024 T or received.

FIGURE 2-5: ISO REFERENCE LAYER MODEL

OSC before data may be transmitted

OSI REFERENCE LAYERS

Application

Presentation

Session

Transport

Network

Data Link Layer

2.9 Network Layering Reference Model

Figure 2-5 shows the ISO Network Layering Reference

Model. The shaded areas are implemented by the MCP2150, the cross-hatched area is implemented by an infrared transceiver. The unshaded areas should be implemented by the Host Controller.

Has to be implemented in Host Controller firmware (such as a PICmicro microcontroller)

Regions implemented by the MCP2150

Regions implemented by the Optical Transceiver logic

LLC (Logical Link Control) Acceptance Filtering Overload Notification Recovery Management

MAC (Medium Access Control) Data Encapsulation/Decapsulation Frame Coding (stuffing, destuffing) Medium Access Management Error Detection Error Signalling Acknowledgment Serialization/Deserialization

Physical Layer

PLS (Physical Signalling)

Bit Encoding/Decoding Bit Timing Synchronization

PMA (Physical Medium Attachment) Driver/Receiver Characteristics

MDI (Medium Dependent Interface) Connectors

Supervisor

Fault confinement (MAC-LME)

Bus Failure management (PLS-LME)

DS21655B-page 10

Preliminary  2002 Microchip Technology Inc.

MCP2150

The IrDA standard specifies the following protocols:

• Physical Signaling Layer (PHY)

• Link Access Protocol (IrLAP)

• Link Management Protocol/Information Access Service (IrLMP/IAS)

The IrDA data lists optional protocols. They are:

•Tiny TP

• IrTran-P

• IrOBEX

•IrLAN

•IrCOMM

•IrMC

•IrDA Lite

Figure 2-6 shows the IrDA data protocol stack and

which components are implemented by the MCP2150.

FIGURE 2-6: IRDA DATA - PROTOCOL

STACKS

IrTran-P IrObex IrLan IrMC

LM-IAS Tiny Transport Protocol (Tiny TP)

IR Link Management - Mux (IrLMP)

IR Link Access Protocol (IrLAP)

Asynchronous

Serial IR

(9600 -115200 b/s)

Supported by the MCP2150

(2)

Synchronous

IrComm

Serial IR

(1.152 Mb/s)

Optional IrDA data protocols not supported by the MCP2150

(1)

Synchronous

4 PPM

(4 Mb/s)

2.9.1 IrDA DATA PROTOCOLS SUPPORTED BY MCP2150

The MCP2150 supports these required IrDA standard protocols:

• Physical Signaling Layer (PHY)

• Link Access Protocol (IrLAP)

• Link Management Protocol/Information Access

Service (IrLMP/IAS)

The MCP2150 also supports some of the optional protocols for IrDA data. The optional protocols that the MCP2150 implements are:

•Tiny TP

•IrCOMM

2.9.1.1 Physical Signal Layer (PHY)

The MCP2150 provides the following Physical Signal Layer specification support:

• Bidirectional communication

• Data Packets are protected by a CRC

- 16-bit CRC for speeds up to 115.2 kbaud

• Data Communication Rate

- 9600 baud minimum data rate

The following Physical Layer Specification is dependant on the optical transceiver logic used in the application. The specification states:

• Communication Range, which sets the end user

expectation for discovery, recognition and performance.

- Continuous operation from contact to at least 1 meter (typically 2 meters can be reached)

- A low power specification reduces the objective for operation from contact to at least 20 cm (low power and low power) or 30 cm (low power and standard power).

Note 1: The MCP2155 implements the 9-wire

“cooked" service class serial replicator.

2: An optical transceiver is required.

 2002 Microchip Technology Inc. Preliminary

DS21655B-page 11

MCP2150

2.9.1.2 IrLAP

The MCP2150 supports the IrLAP protocol. The IrLAP protocol provides:

• Management of communication processes on the link between devices.

• A device-to-device connection for the reliable, ordered transfer of data.

• Device discover procedures.

• Hidden node handling.

Figure 2-7 identifies the key parts and hierarchy of the

IrDA protocols. The bottom layer is the Physical layer, IrPHY. This is the part that converts the serial data to and from pulses of IR light. IR transceivers can’t transmit and receive at the same time. The receiver has to wait for the transmitter to finish sending. This is sometimes referred to as a “Half-Duplex” connection. The IR Link Access Protocol (IrLAP) provides the structure for packets (or “frames”) of data to emulate data that would normally be free to stream back and forth.

FIGURE 2-7: IRDA STANDARD

PROTOCOL LAYERS

Host O.S. or Application

IrCOMM

IrLMP – IAS

IrLAP

Protocols resident in

MCP2150

Figure 2-8 shows how the IrLAP frame is organized.

The frame is proceeded by some number of Beginning of Frame characters (BOFs). The value of the BOF is generally 0xC0, but 0xFF may be used if the last BOF character is a 0xC0. The purpose of multiple BOFs is to give the other station some warning that a frame is coming.

The IrLAP frame begins with an address byte (“A” field), then a control byte (“C” field). The control byte is used to differentiate between different types of frames and is also used to count frames. Frames can carry status, data or commands. The IrLAP protocol has a command syntax of it’s own. These commands are part of the control byte. Lastly, IrLAP frames carry data. This data is the information (or “I”) field. The integrity of the frame is ensured with a 16-bit CRC, referred to as the Frame Check Sequence (FCS). The 16-bit CRC value is transmitted LSB first. The end of the frame is marked with an EOF character, which is always a 0xC1. The frame structure described here is used for all versions of IrDA protocols used for serial wire replacement for speeds up to 115.2 kbaud.

Note 1: Another IrDA standard that is entering

general usage is IR Object Exchange (IrOBEX). This standard is not used for serial connection emulation.

2: IrDA communication standards faster

than 115.2 kbaud use a different CRC method and physical layer.

FIGURE 2-8: IRLAP FRAME

IrPHY

IR pulses transmitted and received

X BOFs BOF A C FCSI EOF

(1+N) of C0h payload

In addition to defining the frame structure, IrLAP provides the “housekeeping” functions of opening, closing and maintaining connections. The critical parameters that determine the performance of the link are part of this function. These parameters control how many BOFs are used, identify the speed of the link, how fast either party may change from receiving to transmitting, etc. IrLAP has the responsibility of negotiating these parameters to the highest common set so that both sides can communicate as quickly, and as reliably, as possible.

bytes

C1h

DS21655B-page 12

Preliminary  2002 Microchip Technology Inc.

MCP2150

2.9.1.3 IrLMP

The MCP2150 implements the IrLMP protocol. The IrLMP protocol provides:

• Multiplexing of the IrLAP layer. This allows multiple channels above an IrLAP connection.

• Protocol and service discovery. This is via the Information Access Service (IAS).

When two devices that contain the IrDA standard feature are connected, there is generally one device that has something to do and the other device that has the resource to do it. For example, a laptop may have a job to print and an IrDA standard compatible printer has the resources to print it. In IrDA standard terminology, the laptop is a Primary device and the printer is the Secondary device. When these two devices connect, the Primary device must determine the capablities of the Secondary device to determine if the Secondary device is capable of doing the job. This determination is made by the Primary device asking the Secondary device a series of questions. Depending on the answers to these questions, the Primary device may or may not elect to connect to the Secondary device.

The queries from the Primary device are carried to the Secondary device using IrLMP. The responses to these queries can be found in the Information Access Service (IAS) of the Secondary device. The IAS is a list of the resources of the Secondary device. The Primary device compares the IAS responses with its requirements and then makes the decision if a connection should be made.

The MCP2150 identifies itself to the Primary device as a modem.

2.9.1.4 Link Management - Information Access Service (LM-IAS)

The MCP2150 implements the LM-IAS. Each LM-IAS entity maintains an information database to provide:

• Information on services for other devices that

contain the IrDA standard feature (Discovery).

• Information on services for the device itself.

• Remote accessing of another device’s information

base.

This is required so that clients on a remote device can find configuration information needed to access a service.

2.9.1.5 Tiny TP

Tiny TP provides the flow control on IrLMP connections. An optional service of Segmentation and Reassembly can be handled.

2.9.1.6 IrCOMM

IrCOMM provides the method to support serial and parallel port emulation. This is useful for legacy COM applications, such as 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 (printer) connections of various capabilities. The MCP2150 supports the 9-wire “cooked” service class of IrCOMM. Other service classes supported by IrCOMM are shown in Figure 2-9.

Note: The MCP2150 identifies itself as a modem

to ensure that it is identified as a serial device with a limited amount of memory.

The MCP2150 is not a modem, and the non-data circuits are not handled in a modem fashion.

FIGURE 2-9: IRCOMM SERVICE CLASSES

IrCOMM Services

Uncooked Services Cooked Services

Parallel Serial

IrLPT

Supported by MCP2150

3-wire Raw

Parallel

Centronics

IEEE 1284

Serial

3-wire Cooked

9-wire Cooked

 2002 Microchip Technology Inc. Preliminary

DS21655B-page 13

MCP2150

2.9.2 OTHER OPTIONAL IrDA DATA PROTOCOLS

Other IrDA data protocols have been developed to specific application requirements. These optional protocols are not supported by the MCP2150. These IrDA data protocols are briefly described in the following sub-sections. For additional information, please refer to the IrDA website (www.IrDA.org).

2.9.2.1 IrTran-P

IrTran-P provides the protocol to exchange images with digital image capture devices/cameras.

2.9.2.2 IrOBEX

IrOBEX provides OBject EXchange services. This is similar to HTTP.

2.9.2.3 IrLAN

IrLAN describes a protocol to support IR wireless access to a Local Area Network (LAN).

2.9.2.4 IrMC

IrMC describes how mobile telephony and communication devices can exchange information. This information includes phonebook, calender and message data.

Also how call control and real-time voice are handled (RTCON).

2.9.2.5 IrDA Lite

IrDA Lite describes how to reduce the application code requirements, while maintaining compatibility with the full implementation.

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Preliminary  2002 Microchip Technology Inc.

MCP2150

2.9.3 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 protocol 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 protocols. The MCP2150 supports elements of this IrDA 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 2-10 shows the connection sequence.

2.9.3.1 Normal Disconnect Mode (NDM)

When two IrDA standard compatible devices come into range they must first recognize each other. The basis of this process is that one device has some task to accomplish and the other device has a resource needed to accomplish this task. One device is referred to as a Primary device and the other is referred to as a Secondary device. This distinction between Primary device and Secondary device is important. It is the responsibility of the Primary device to provide the mechanism to recognize other devices. So the Primary device must first poll for nearby IrDA standard compatible devices. During this polling, the defaut baud rate of 9600 baud is used by both devices.

For example, if you want to print from an IrDA equipped laptop to an IrDA printer, utilizing the IrDA standard feature, you would first bring your laptop in range of the printer. In this case, the laptop is the one that has something to do and the printer has the resource to do it. The laptop is called the Primary device and the printer is the Secondary device. Some data-capable cellphones have IrDA standard infrared ports. If you used such a cellphone with a Personal Dig-

ital Assistant (PDA), the PDA that supports the IrDA standard feature would be the Primary device and the cellphone would be the Secondary device.

When a Primary device polls for another device, a nearby Secondary device may respond. When a Secondary device responds, the two devices are defined to be in the Normal Disconnect Mode (NDM) state. NDM is established by the Primary device broadcasting a packet and waiting for a response. These broadcast packets are numbered. Usually 6 or 8 packets are sent. The first packet is number 0, the last packet is usually number 5 or 7. Once all the packets are sent, the Primary device sends an ID packet, which is not numbered.

The Secondary device waits for these packets and then responds to one of the packets. The packet it responds to determines the “time slot” to be used by the Secondary device. For example, if the Secondary device responds after packet number 2, then the Secondary device will use time slot 2. If the Secondary device responds after packet number 0, then the Secondary device will use time slot 0. This mechanism allows the Primary device to recognize as many nearby devices as there are time slots. The Primary device will continue to generate time slots and the Secondary device should continue to respond, even if there’s nothing to do.

Note 1: The MCP2150 can only be used to

implement a Secondary device.

2: The MCP2150 supports a system with

only one Secondary device having exclusive use of the IrDA standard infrared link (known as "point-to-point" communication).

3: The MCP2150 always responds to packet

number 2. This means that the MCP2150 will always use time slot 2.

4: If another Secondary device is nearby,

the Primary device may fail to recognize the MCP2150, or the Primary device may not recognize either of the devices.

During NDM, the MCP2150 handles all of the responses to the Primary device (Figure 2-10) without any communication with the Host Controller. The Host Controller is inhibited by the CTS signal of the MCP2150 from sending data to the MCP2150.

 2002 Microchip Technology Inc. Preliminary

DS21655B-page 15

MCP2150

2.9.3.2 Discovery Mode

Discovery mode allows the Primary device to determine the capabilities of the MCP2150 (Secondary device). Discovery mode is entered once the MCP2150 (Secondary device) has sent an XID response to the Primary device and the Primary device has completed sending the XIDs and then sends a Broadcast ID. If this sequence is not completed, then a Primary and Secondary device can stay in NDM indefinitely.

When the Primary device has something to do, it initiates Discovery. Discovery has two parts. They are:

• Link initialization

• Resource determination

The first step is for the Primary and Secondary devices to determine, and then adjust to, each other’s hardware capabilities. These capabilities are parameters like:

• Data rate

• Turn around time

• Number of packets without a response

• How long to wait before disconnecting

Both the Primary and Secondary device begin communications at 9600 baud, which is the default baud rate. The Primary device sends its parameters, then the Secondary device responds with its parameters. For example, if the Primary supports all data rates up to

115.2 kbaud and the Secondary device only supports

19.2 kbaud, the link will be established at 19.2 kbaud.

Note: The MCP2150 is limited to a data rate of

115.2 kbaud.

Once the hardware parameters are established, the Primary device must determine if the Secondary device has the resources it requires. If the Primary device has a job to print, then it must know if it’s talking to a printer, not a modem or other device. This determination is made using the Information Access Service (IAS). The job of the Secondary device is to respond to IAS queries made by the Primary device. The Primary device must ask a series of questions like:

• What is the name of your service?

• What is the address of this service?

• What are the capabilities of this device?

When all the Primary device’s questions are answered, the Primary device can access the service provided by the Secondary device.

During Discovery mode, the MCP2150 handles all responses to the Primary device (see Figure 2-10) without any comm unication with the Host Controller. The Host Controller is inhibited by the CTS signal of the MCP2150 from sending data to the MCP2150.

2.9.3.3 Normal Connect Mode (NCM)

Once discovery has been completed, the Primary device and MCP2150 (Secondary device) can freely exchange data.

The MCP2150 can receive IR data or serial data, but not both simultaneously. The MCP2150 uses a hardware handshake to stop the local serial port from sending data while the MCP2150 is receiving IR data.

Note: Data loss will result if this hardware

handshake is not observed.

Both the Primary device and the MCP2150 (Secondary device) check to make sure that data packets are received by the other without errors. Even when data is required to be sent, the Primary and Secondary devices will still exchange packets to ensure that the connection hasn’t, unexpectedly, been dropped. When the Primary device has finished, it then transmits the close link command to the MCP2150 (Secondary device). The MCP2150 will confirm the close link command and both the Primary device and the MCP2150 (Secondary device) will revert to the NDM state.

Note: If the NCM mode is unexpectedly termi-

nated for any reason (including the Primary device not issuing a close link command), the MCP2150 will revert to the NDM state 10 seconds after the last frame has been received.

It is the responsability of the Host Controller program to understand the meaning of the data received and how the program should respond to it. It’s just as if the data were being received by the Host Controller from a UART.

DS21655B-page 16

Preliminary  2002 Microchip Technology Inc.

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