A fast, simple microcomputer-controlled data acquisition system

A simple data acquisition scheme has been designed for the TI9900 microcomputer which will simultaneously acquire and store the output of two independent 8-bit, Analog-to-Digital Converters (ADC's) during a single programmed “move” instruction cycle. The ADC is read during the indirectly addressed read part of the “move” cycle and the start conversion is initiated during the indexed indirectly addressed write part of the “move” cycle. For a TI9900 with a 3-MHz clock this provides data acquisition at a 115-kHz rate. The high-speed data acquisition is made possible by configuring the interface to respond to two separate nonconflicting parallel processes. Triggering for the two parallel processes occurs sequentially and is derived from the seven memory accesses of the mov instruction; a read A-to-D signal and a start conversion signal. The hardware/software interfacing requirements and assembler instructions used to control the acquisition are described.