## Alan R. Baldwin

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I joined the Physics Department at Kent State University in January of 1976 as the staff electronics engineer. Since then I have been involved with the development of data-acquisition systems for neutron time-of-flight spectrometry, nuclear magnetic resonance, AC calorimetry, x-ray spectroscopy, and light scattering in the Physics Department and the Liquid Crystal Institute.

Additional instrumentation development included many NIM (Nuclear Instrument Module) high-speed analog and digital instruments: 350 MHz display scalers, analog fanout and summing modules, AND/NAND and OR/NOR logic modules, neutron-gamma pulse-shape discriminator systems, and a photomultiplier tube stabilization system using pulsed blue light emitting diodes. Other instrumentation include four photon counting time correlators with acquisition bin widths from 1 nanosecond to seconds, graphic display and plotting systems, and an array processor for nuclear spectrometry data with a throughput of 128M operations per second (built in 1982) for realtime histogram construction.

A personal project begun in 1976 is perhaps my most ambitious: the design of a general purpose mini-computer. The computer took about two years of spare time to design and build. The machine has a 32-bit wide microcoded instruction decoder and a 96-bit wide microcoded sequencer with a basic microcycle time of 250 nanoseconds. The 32-bit CPU uses 8 AMD-2901C 4-bit slice arithmetic/logic units wired to perform 8, 16, 24, and 32-bit operations. The machine has 4K words of instruction decoder and sequencer microcode. The machine was coded to emulate the venerable PDP-11/34 instruction set and used UNIBUS I/O. Additionally the FP-11 and FIS (PDP-11/35) floating point were also coded. The basic PDP-11 instruction set programmed in 256 words of decoder and sequencer microcode. The EIS, FIS, and FPU microcode required 768 additional sequencer words. This code was programmed into bipolar proms as the machines native instruction set. The remaining 3K of decoder and sequencer microcode was high-speed programmable static ram which could be loaded on the fly with whatever extension instructions you might wish to implement (e.g. a block memory-to-memory move instruction). The machine could execute most single operand register and double operand register-to-register instructions in .75 microseconds (3 microcycles). The machine was benchmarked at slightly faster than the PDP-11/34 (with a FPU). This machine was my development platform for many microprocessor based projects and ran RT-11/TSX-Plus.

Other work from the mid 1980's through the late 1990's has included PC based data-acquisition systems for an EPR spectrometer and for measurements of current-voltage characteristics of high-temperature superconducting materials. These projects were programmed in Visual Basic, assembly, and C/C++ using IEEE-488 and DLL routines for I/O. Another project was the development of microprocessor simulators (for WIN 3.xx and WIN95) for use in our microprocessor design courses. Currently simulators exist for the Motorola 6800 and 6809, Intel 8088, and the Hitachi H8/3xx microprocessors.

The most recent work has been the design of high-speed auto and cross-correlators for analyzing laser light scattering from liquid-crystal molecules. These correlators have time resolutions of 1.0 nanoseconds, 125 picoseconds, and 62.5 picoseconds. Their distinguishing characteristics include continuous realtime correlation, wide dynamic range of simultaneously generated correlation spectra: 62.5 picoseconds per channel to 10 seconds per channel, and automatic internal and external timing calibration.

In parallel with the preceeding projects the development of the "TCP/IP Package for TSX-Plus" and the "ASxxxx Cross Assemblers" has been a continued pleasure.

### Academics

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1970/1971 BS/MS Electrical Engineering, Clarkson University

1973/1994 MA/PhD Physics, Kent State University

Co-authored/authored over 80 publications in instrumentation and nuclear physics. Co-authored a book entitled "16-Bit Microprocessors" published by Howard W. Sams & Co., Inc. (1981).

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... baldwin@shop-pdp.kent.edu

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Last Updated: January 2006