A two-pass TMS320C25 for the Motorola EXORMacs Rabin Deka, B Singh* and I A Glover* demonstrate the use of a host microcomputer for developing digital signal processing software This paper describes the development of a cross-assembler, denoted XTIC25, which runs on Motorola's EXORMacs system. First a suitable data format called TIC25 is derived from the TMS320C25 digital signal microprocessor. This data format is then used in conjunction with software written using a combination of subsets of Pascal and MC68000 assembler routines, based on a two-pass algoflthm. The cross-assembler is validated using several test programs and is capable of developing software, using the TMS320C25 assembler, within a microcomputer environment. In this way, the use of a host microcomputer for developing digital signal processing software is demonstrated. cross-assembler digital signal microprocessor data format microcomputer serialalgorithm TM5320C25 Several applications in digital signal processing (DSP) demand the implementation of high speed digital signal microprocessors (DSMs), also denoted by DSP devices. Their ability to be interfaced with A/D and D/A, converters, multiplexers and de-multiplexers, and the availability of engineering support and software development tools is also important. During recent years, the implementation of DSMs has been attracting a great deal of academic, industrial and research interest. Today, institutions wishing to take advantage of DSMs can choose from an ever growing variety of devices. The choice of device, however, needs care. The processor's throughput, address space, arith- metic precision and benchmark performance must be considered. The TMS320C25 is one of the most popular currently available DSMs. Room 208 Nikko Palace,4-24-13 Tsurumaki, Setagaya-ku, Tokyo 154, Japan *Department of Electrical Engineering,University of Bradford, Bradford, West Yorkshire, BD7 IDP, UK Paper received: 24 July 1991. Revised: 4 February1992 THE TMS320C25 DSM The TMS320C251 is a general purpose and partially static ~ DSM made by Texas Instruments, capable of operating at any frequency within the range 6.7 MHz to 40.9 MHz. It is also sub-coherent I to other members of the TMS32011x family DSMs. Any processors in this family support real-time DSP and computation-intensive appli- cations in the areas of telecommunications, modems, speech processing, graphics, image processing, spectrum analysis, audio processing, digital filtering, high speed control, instrumentation and numerical processing. The TMS320C25 is a pin compatible CMOS version of the TMS320201 with a faster instruction cycle time and the inclusion of additional hardware, e.g., on-chip program memory, and software, e.g., additional instructions and features. It is also completely object code compatible with the TMS32020. Table 1 summarizes some useful information about this family. Serial algorithm The term serial algorithm is used here to denote a general purpose assembler algorithm which uses two basic passes to complete the translation process of a source program. A, flow chart for this algorithm is included in Reference 3, and Appendix A is a particular implementation. In the first pass, an assembler assigns a location to each instruction and data-defining pseudo-instruction, and thus defines values of symbols appearing in the label field of the source program. Initially, the location counter is set If for a DSM,there is a lower frequencylimit, fl, suchthat, 0 < fl < fu,and no performance degradation occursat any frequency within the limits fl and fu, then the DSM can be termed asa partially static DSM; Reference 2 includes more information 1If the instruction set of a DSM and its associated machine code and pin configurations are sub-set(s)of the related set(s)of one or more DSM(s), then the first DSM can be termed sub-coherent to the other(s); Reference 2 includes more information 0141-9331/92/030133-08 © 1992 Butterworth-Heinemann Ltd Vol 16 No 3 1992 133