SPASTIC - A System for Programming Angles, Scalar, and Timer by Internal Counting

摘要

SPASTIC is a modification of the FOCAL interpreter designed to control a simple PDP-8L interface for X-ray diffraction experiments. Control operations are accessed through a set of FOCAL functions which control four stepping motors, an internal data-break scalar, a timer based on a crystal clock interrupt, and the X-ray shutter solenoid. Counting of motor pulses, timer pulses, and scalar pulses are all accomplished within the computer to minimize the interface hardware. The system is used to control an Advanced Metals Research low-angle X-ray diffractometer, using one motor for the 2 theta drive and a second for the attenuator wheel. Programs have been written for zeroing in on the primary beam and for step-scanning through 2 theta, taking data points at various 2 theta intervals. The use of FOCAL permits flexibility in the design of experiments by facilitating the programming and the debugging. (Author