Overview of Popular DSP Architectures: TI, ADI, Motorola R.C. Maher ECEN4002/5002 DSP Laboratory Spring 2003

ECEN4002 Spring 2003Other DSP Architectures R. C. Maher2 Introduction Most DSP microprocessor architectures share the common features: fast MAC with guard bits, Harvard architecture, and parallel compute/moves Alternatives have to do with number and size of registers, on-chip memory, variety of instructions, and pipelining Most common DSP architectures have “legacy baggage:” new designs must be compatible with older designs to allow code re-use

ECEN4002 Spring 2003Other DSP Architectures R. C. Maher3 Motorola 563xx As we know from the lab assignments, the Motorola 563xx has the following characteristics: –24-bit word size, dual 56-bit accumulators –X,Y,P data buses –8 DAG registers (linear, modulo, reverse) –4 general registers –Integrated MAC/ALU (no parallel computation)

ECEN4002 Spring 2003Other DSP Architectures R. C. Maher4 “Old” TI TMS320 The Texas Instruments TMS320 family appeared in the early 1980s –16-bit word size, single 32-bit accumulator –D,P data buses –5 aux registers (data or address) –No modulo support –Integrated MAC/ALU (no parallel computation)

ECEN4002 Spring 2003Other DSP Architectures R. C. Maher5 Example TMS320 Code LAC XN,15 * load accumulator with shift LT D1NM1 * load T register with state MPY A11 * multiply with coef LTA D1NM2 * load T with next state MPY A21 * multiply with coef APAC * accumulate product SACH D1N,1 * store result with shift

ECEN4002 Spring 2003Other DSP Architectures R. C. Maher6 “New” TI C54x –16-bit word size, 17x17 multiply, dual 40-bit accumulators –1 Prog, 3 Data, 4 Address buses –8 auxiliary registers (linear, modulo, reverse) –Integrated MAC/ALU (no parallel computation) TI also makes floating point ‘C30 and C6x parts

ECEN4002 Spring 2003Other DSP Architectures R. C. Maher7 “Old” ADI 21xx Analog Devices original DSP family was organized as follows: –16-bit word size, single 40-bit accumulator –D,P data buses (16-bit data, 24-bit program) –10 general purpose registers –Dual 4-register DAGs (similar to 563xx) –Separate ALU, MAC, and SHIFT (for parallel computation) –“Shadow” registers for fast context switching

ECEN4002 Spring 2003Other DSP Architectures R. C. Maher8 ADI Assembly Language Motorola and TI use a register transfer assembly language format Move x0,y0 Add x0,b Mac x0,y0,a ADI uses an algebraic assembly language AX0 = MR1 AR=AX0+AY0 MR=MR+MX0*MY0

ECEN4002 Spring 2003Other DSP Architectures R. C. Maher9 ADI Floating point “Sharc” ADI Sharc (super Harvard architecture) –16 40-bit GP registers –32-bit or 40-bit IEEE floating point representation, and fixed point math, too –D,P buses –Dual DAGs

ECEN4002 Spring 2003Other DSP Architectures R. C. Maher10 “New” ADI/Intel Blackfin Dual 16-bit MACs, 2 40-bit ALUs, 4 8-bit “video” ALUs Dual DAGs, which include base, length, and offset registers (no “power-of-two” alignment) 8 GP registers Many flexible parallel operations on various data types/lengths

ECEN4002 Spring 2003Other DSP Architectures R. C. Maher11 DSP-like Features for GP micros DSP algorithms often fit a “single instruction, multiple data” (SIMD) framework Intel, AMD, and Motorola have DSP-like instruction extensions on their processors (MMX, SSE, 3D-NOW, Altivec, etc.) Most of these do not support a true MAC with guard bits

ECEN4002 Spring 2003Other DSP Architectures R. C. Maher12 Conclusion DSP design has evolved to include parallel computation hardware, flexible addressing, and more processor registers Common embedded system designs now have a general purpose processor coupled with a DSP core Compilers for DSPs are still evolving: usually compile the code, profile it, then hand code inner loops and “hot spots”