Last revision: 8/25/03 Programmable Digital

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Last revision: 8/25/03 
Programmable Digital 
Signal Processor (PDSP): A 
Survey 
Surin Kittitornkun
and Yu Hen Hu 
University of Wisconsin - Madison 
Department of Electrical and Computer Engineering 
1415 Engineering Drive 
Madison, WI 53706 
[e-mail] 
1. Introduction 
Programmable digital signal processors (PDSPs) are general-purpose microprocessors designed 
specifically for digital signal processing (DSP) applications. They contain special instructions 
and special architecture supports so as to execute computation-intensive DSP algorithms more 
efficiently.
PDSPs are designed mainly for embedded DSP applications. As such, the user may never 
realize the existence of a PDSP in an information appliance. Important applications of PDSPs 
include modem, hard drive controller, cellular phone data pump, set-top box, etc.
The categorization of PDSPs falls between the general-purpose microprocessor and the custom-
designed, dedicated chip set. The former have the advantage of ease of programming and 
development. However, they often suffer from disappointing performance for DSP applications 
due to overheads incurred in both the architecture and the instruction set. Dedicated chip sets, 
on the other hand, lack the flexibility of programming. The time to market delay due to chip 
development may be longer than the program coding of programmable devices.

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Last revision: 8/25/03 
1.A A Brief Historical Scan of PDSP Development 
1.A.1 1980s to 1990s 
A number of PDSPs appeared in the commercial market in the early 1980s. Intel introduced the 
Intel2920 around 1980 featuring on-chip A/D (analog-to-digital) and D/A (digital-to-analog) 
converters. Nonetheless, it had no hardware multiplier and was difficult to load program 
parameters into the chip due to the lack of digital interface. In nearly the same time, NEC 
introduced the NEC MPD7720. It is equipped with a hardware multiplier, and is among the first 
to adopt the Harvard architecture with physically separate on-chip data memory and program 
memory. Texas Instrument introduced the TMS320C10 in 1982. Similar to the MPD7720, the 
‘C10 adopts the Harvard architecture and has a hardware multiplier. Furthermore, the ‘C10 is 
the first PDSP that can execute instructions from off-chip program memory without 
performance penalty due to off-chip memory input/output (I/O). This feature brought PDSPs 
closer to the microprocessor/microcontroller programming model. In addition, the emphasis on 
development tools and libraries by Texas Instrument led to wide spread applications of PDSP. 
The architectural features of several representative examples of these early PDSP chips are 
summarized in Table 1. 
Table 1. Summary of characteristics of early PDSP