TMS320C25 SPRA077 TMS320 RS-232

Software UART Using the TMS320C25 APPLICATION REPORT: SPRA077 David Zalac Digital Signal Processor ProductsSemiconductor Group

An Implementation of a Software UART Using the TMS320C25 TMS320C25 APPLICATION REPORT: SPRA077 SPRA077 David Zalac Digital Signal Processor ProductsSemiconductor Group Texas Instruments Digital Signal Processing Solutions IMPORTANT NOTICE Texas Instruments (TI) reserves the right to make changes to its products or to discontinue any semiconductor product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current. TI warrants performance of its semiconductor products and related software to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are utilized to the extent TI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. Certain application using semiconductor products may involve potential risks of death, personal injury, or severe property or environmental damage ("Critical Applications"). TI SEMICONDUCTOR PRODUCTS ARE NOT DESIGNED, INTENDED, AUTHORIZED, OR WARRANTED TO BE SUITABLE FOR USE IN LIFE-SUPPORT APPLICATIONS, DEVICES OR SYSTEMS OR OTHER CRITICAL APPLICATIONS. Inclusion of TI products in such applications is understood to be fully at the risk of the customer. Use of TI products in such applications requires the written approval of an appropriate TI officer. Questions concerning potential risk applications should be directed to TI through a local SC sales office. In order to minimize risks associated with the customer's applications, adequate design and operating safeguards should be provided by the customer to minimize inherent or procedural hazards. TI assumes no liability for applications assistance, customer product design, software performance, or infringement of patents or services described herein. Nor does TI warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of TI covering or relating to any combination, machine, or process in which such semiconductor products or services might be or are used. Copyright © 1997, Texas Instruments Incorporated TRADEMARKS TI is a trademark of Texas Instruments Incorporated. Other brands and names are the property of their respective owners. CONTACT INFORMATION US TMS320 TMS320 HOTLINE (281) 274-2320 US TMS320 TMS320 FAX (281) 274-2324 US TMS320 TMS320 BBS (281) 274-2323 US TMS320 TMS320 email dsph@ti.com An Implementation of a Software UART Using the TMS320C25 TMS320C25 Abstract When transmitting to and receiving data from a processing engine such as the TMS320C25 TMS320C25 digital signal processor, it is common to encounter problems when interfacing to asynchronous devices. This chapter provides a look at software implementation of a Universal Asynchronous Receiver and Transmitter (UART) which enables communication with asynchronous serial devices with a minimum of external hardware. Topics covered include: q Characteristics of asynchronous communications q Limitations of and reasons where use of a UART are justifiable q An overview of the functions provided by a UART q UART Implementation q A list of References q An appendix of source code Supporting figures illustrate the following: q UART word format and architecture q Timer interrupt service routine q Transmitter routine q UART status word q Receiver routine q RS-232 RS-232 interface SPRA077 SPRA077 Product Support World Wide Web Our World Wide Web site at www.ti.com contains the most up to date product information, revisions, and additions. New users must register with TI&ME before they can access the data sheet archive. TI&ME allows users to build custom information pages and receive new product updates automatically via email. Email For technical issues or clarification on switching products, please send a detailed email to dsph@ti.com. Questions receive prompt attention and are usually answered within one business day. 6 An Implementation of a Software UART Using the TMS320C25 TMS320C25