VLSI Digital Signal Processing Systems: Design and Implementation

1.4    REPRESENTATIONS OF DSP ALGORITHMS

DSP algorithms are described by nonterminating programs which execute the same code repetitively. For example, a 3-tap FIR digital filter described by the non-terminating program

Execution of all the computations in the algorithm once is referred to as an iteration. The iteration period is the time required for execution of one iteration of the algorithm. The iteration rate is the reciprocal of the iteration period. During each iteration, the 3-tap FIR filter in (1.60) processes one input signal, completes 3 multiplication and 2 addition operations (in serial or in parallel), and generates 1 output sample. DSP systems are also characterized by the sampling rate (also referred to as throughput) in terms of number of samples processed per second. The critical path of a combinational logic circuit is defined as the longest path between inputs and outputs, where the length of a path is proportional to its computation time. DSP systems generally are implemented using sequential circuits, where the critical path is defined as the longest path between any two storage elements (or delay elements). The critical path computation time determines the minimum feasible clock period of a DSP system. The latency is defined as the difference between the time an output is generated and the time at which its corresponding input was received by the system. For ...