Modem Code for Group 3 Fax (TMS320C5x/'C25) by ILLICO! Software Overview ILLICO is offering digital signal processing software modules for the TMS320 fixed-point family that implement the CCITT modem standards for Group 3 FAX: V.21, V.27ter, V.29, and V.17. A single software package supports both the TMS320C5x and the TMS320C25 processors. A software switch set at assembly time selects the target processor. The TMS320C25 assembled version supports other TI products which execute the TMS320C25 instruction set (TMS320C2xx, MSP58C80). These software modems can replace conventional FAX modem chip sets in applications where a general-purpose fixed-point DSP is available on a dedicated or shared basis. Digital sample interpolation permits direct "all digital" interface with 64-kbps PCM data streams and avoids conversion to an analog signal. For analog environments, a simple m- or A-law codec provides the analog interface. Page-oriented variable addressing allows easy implementation of multiple independent modems in one processor. The target applications for these software modems are FAX relay, interactive voice response systems, store-and-forward FAX servers, and multimedia communications. All available code was created by ILLICO's staff and can be customized to support special interfaces and special signal processing requirements. Features and Benefits • Modem code callable with C-language or assembly language conventions. • Zero-overhead context switching for multiple modems in one processor. • HDLC coding for both V.21 and image frames (option). • Detection of start and end of echo protection tone. • Receiver interpolation to support fixed sampling rates. • Block-oriented I/O to facilitate processor sharing with other applications. • Detection of V.21 signals in QAM receiver mode. • Diagnostic mean-square-error calculation and eye-pattern support. • Transmit speed tracking by sample interpolation (option). • Forty-page Interface Specification to aid installation and application creation. Processor and System Requirements The following values represent the nominal resource usage. The ranges of MIP performance depend on the level of internal RAM usage. • Data RAM per channel 256 words internal (data variable block) 84 words internal or external (equalizer tap block) 328 words external (V.17 only; trellis decoder block) • Program memory 5 k total for V.21, V.27ter, V.29 8 k total for V.21, V.27ter, V.29, and V.17 • Per channel MIPs loading (Million Instructions per Second, zero wait state) 5.3 MIPs (±10%) for V.29/V.27ter/V.21 receivers 9.5 MIPs (±10%) for V.17 receiver Algorithm Verification The ILLICO FAX modem code implements all of the features of CCITT Recommendations V.21, V.27ter, V.29, and V.17 needed to support Group 3 FAX (CCITT T.4 and T.30). Performance measurements and acceptance tests are performed using simultaneous parallel testing against Rockwell modem cards. Test impairments are generated by the T.A.S. Model 182 Network Emulator. A demonstration/evaluation board with integral test capabilities is available for purchase as part of the software license. Availability The TMS320 fixed-point modem code is available now under a royalty-free licensing arrangement which includes a source-code option. Demonstrations are available at ILLICO's offices in Santa Clara, California. Company Background and Contact Information ILLICO is a software development and licensing firm specializing in the application of digital signal processing to telecommunications product development. We have been active for over seven years with U.S. and international clients, principally in the area of voice band modem design. All ILLICO products were created by ILLICO's staff and are typically modified to meet special client requirements. Contact: Lien Nguyen ILLICO! 2700 Augustine Drive Suite 145 Santa Clara, California 95054 (408) 980-8179 Fax: (408) 980-9327 |