Data Throughput and the MCP215X

AN927 M Data Throughput and the MCP215X In many typical systems, the majority of data will travel Author: Mark Palmer either in one direction or the other. That is, the majority Microchip Technology Inc. of data will be transmitted (downloaded) from the Primary Device (PDA) to the Secondary Device (embedded system), or will be transmitted (uploaded) INTRODUCTION from the Secondary Device (embedded system) to the Throughput is based on many factors, some of which Primary Device (PDA). are determined by the Secondary Device (host Typical downloading application examples include: controller + MCP215X) and others that are determined * Embedded system configuration programming by the Primary Device. * Embedded system firmware update This application note discusses techniques that will ® improve the data transfer throughput between an IrDA The data throughput during downloading cannot be standard Primary Device and embedded system and- controlled by the embedded system's host controller. In focus on what techniques can be used on the interface this case, the data throughput is primarily determined between the host controller and the MCP215X. The by the characteristics of the Primary Device and the embedded system (Secondary Device) uses a hardware characteristics of the MCP215X. The ® MCP215X device for the IrDA standard communica- hardware characteristics of the MCP215X requires the tion (IrCOMM 9-wire "cooked" service class). Figure 1 CRC generation timing and parsing of the incoming IR shows a typical IrDA standard system. Frame. All timing measurements and screen captures in this Typical uploading application examples include: application note are performed using a Palm™ * Data loggers Tungsten™ T2 PDA as the Primary Device. Using a * Diagnostic ports different Primary Device may yield different results. During upload, the host controller firmware can have a significant impact on the data throughput. Data Transfers In cases where small amounts of data are passed Data Transfers can be broken down into three classes: between devices and require user interface input, IR 1. Data downloading throughput requirements are minimized due to the 2. Data uploading human interface. An example of this would be when the PDA sends some codes to the embedded system, 3. Bidirectional which then responds to the codes. The PDA operator then needs to determine what to do next based on this response. So the actual data throughput is not really an issue. FIGURE 1: PALM™ PDA - EMBEDDED SYSTEM BLOCK DIAGRAM ® Embedded System with IrDA Standard Port (Secondary Device)