Microprocessor control of a computed tomography scanner

The OsteoQuant is a computed tomography scanner for the quantitative assessment of bone density. The scanner incorporates three movements, driven by stepping motors. All movements allow synchronization with data collection to guarantee exact relationship of measurement location, measurement interval, and interval duration. The hardware used to generate the necessary timing pulses to motors and detectors is a TM 990/100-MA2 microprocessor. During acceleration and deceleration phases, two or three motors run concurrently to save time, necessitating special external hardware for generating the motor pulse sequence. On power-up of the microprocessor, the position of the scanner is unknown; each motor position-register is zeroed by driving through a position switch. Several status bits are associated with the various power sources of the system to supply a fast path for troubleshooting.<>