An 8085 based STD bus system for digital control applications

The author describes an effort to produce an 8085-based standard (STD) bus system which includes a 16 bit analog (input/output) interface, a digital pulse-width-modulated output, and an RS232C interface to an IBM PC for downloading assembled programs. The main components of the system include an IBM PC, a STD bus card rack with +or-15 V supplies, and 8085 STD bus CPU card, a STD bus keyboard display card, a digital I/O card, a 16 bit analog I/O card, and a digital control card for the analog I/O. There are two possible methods of I/O in a digitally controlled second-order position control loop. The other method uses an analog-to-digital converter for the feedback inputs and a digital-to-analog converter for the servo amplifier output. Another method uses a digital encoder for the feedback inputs and a pulse-width-modulated signal for the servo amplifier output. The purpose of this design is to provide the basic hardware and software for an 8085-based digital control system which can be used for studying the differences between the above two methods of I/O.<>