1. Introduction1.1. ScopeThis physical specification is intended to facilitate the point-to-point communication between electronic devices (e.g., computers and peripherals) using directed half duplex serial infrared communications links through free space. This document specifies the optical media interfaces for Serial Infrared (SIR) datatransmission up to and including 115.2kbit/s, 0.576 Mbit/s, 1.152Mbit/s, 4.0Mbit/s and 16Mbit/s. It contains specifications for the Active Output Interface and the Active Input Interface, and for the overall link. It also contains Appendices covering test methods and implementation examples.Over the past several years several optical link specifications have been developed. This activity has established the advantages of optical interface specifications to define optical link parameters needed to support the defined link performance. Optical interface specifications are independent of technology, apply over the life of the link and are readily testable for conformance. The IrDA serial infrared link specification supports low cost optoelectronic technology and is designed to support a link between two nodes from 0 to at least 1 meter apart (20 cm for low power parts: please see Section 4.1) as shown in Figure 1 (the two ports need not be perfectly aligned).1.2. ReferencesThe following standards either contain provisions that, through reference in this text, constitute provisions of this proposed standard, or provide background information. At the time of publication of this document, the editions and dates of the referenced documents indicated were valid. However, all standards are subject to revision, and parties to agreements based on this proposed standard are encouraged to investigate the possibility of applying the most recent editions of the standards listed below.IrDA (Infrared Data Association) Serial Infrared Link Access Protocol (IrLAP), Version 1.1, June 16, 1996.IrDA (Infrared Data Association) Serial Infrared Link Management Protocol, IrLMP), Version 1.1, January 23, 1996.IrDA (Infrared Data Association) Serial Infrared Physical Layer Measurement Guidelines, Version 1.0, January 16, 1998.IrDA (Infrared Data Association) IrMC Specification, Version 1.0.1, January 10, 1998.2. General Description2.1. Point-to-Point Link OverviewThe serial infrared link supports optical link lengths from zero to at least 1 meter with standard power transceivers (20cm for low power transceivers: see section 4.1) for accurate (within specified bit error ratio), free space communication between two independent nodes (such as a calculator and a printer, or two computers).2.2. EnvironmentThe Optical Interface Specifications apply over the life of the product and over the applicable temperature range for the product. Background light and electric field test conditions are presented in Appendix A.2.3. Modulation SchemesFor data rates up to and including 1.152Mbit/s, RZI modulation scheme is used, and a “0” is represented by a light pulse. For rates up to and including 115.2kbit/s, the optical pulse duration is nominally 3/16 of a bit duration (or 3/16 of a 115.2kbit/s bit duration).For0.576Mbit/s and1.152Mbit/s, the optical pulse duration is nominally 1/4 of a bit duration.For 4.0Mbit/s, the modulation scheme is 4PPM. In it, a pair of bits is taken together and called a data symbol. It is divided into 4 “chips”, only one of which contains an optical pulse. For 4.0Mbit/s, the nominal pulse duration (chip duration) is 125 ns. A “1” is represented by a light pulse.For 16.0Mbit/s transmission, the HHH(1, 13) code a low duty cycle, rate 2/3, (d, k) = (1, 13) runlength limited (RLL) code is used as the modulation code to achieve the specified data rate. The HHH(1, 13) code guarantees for at least one empty chip and at most 13 empty chips between chips containing pulses in the transmitted IR signal.The 16.0Mbit/s rate packet frame structure is based on the current IrDA-FIR(4.0 Mbit/s) frame format with modifications introduced where necessary to accommodate the requirements that are specific to the new modulation code. Furthermore, the HHH(1,13) code is enhanced with a simple scrambling/ descrambling scheme to further optimize the duty cycle.3. Media Interface Description3.1. Physical RepresentationA block diagram of one end of a serial infrared link is shown in Figure 2. Additional signal paths may exist. Because there are many implementation alternatives, this specification only defines the serially encoded optical output and input signals at 3.In the diagram, the electrical signals to the left of the Encoder/Decoder at 1 are serial bit streams. For data rates up to and including 1.152Mbit/s, the optical signals at 3 are bit streams with a 0 being a pulse, and a 1 is a bit period with no pulse. For 4.0Mbit/s, a 4PPM encoding scheme is used, with a “1” being a pulse and a “0” being a chip with no pulse. For 16.0Mbi