Dual slope A/D converter for the 8051

E. SPINELLI; A. VEIGA

Electronic Engineering, Morgan-Grampian House, 30 Calderwood Street, Woolwich, London, SE18 6QH

Morgan-Grampian

Lugar: London; Año: 1996 vol. 01 p. 30 - 30

Based on a previous Applied Idea (A Simple A/D Converter for 8051, E.E. Sept. 1993) a dual slope A/D converter for the 8051 microcontroller is presented. It can work with precisions up to 16 bits without modifications. The circuit consists of a quad opamp, a triple 2- channel analog multiplexer, a voltage reference and a few other components. This N bits A/D converter (the maximum value of N is 16) works as follows: timer 0 is loaded with 216-2N and programmed in Mode 1 with Gate; switch 2 goes to Vx (only positive values are admitted) and this value is integrated. The timer startsto count up when the integrator has an output greater than zero. When the timer interrupt is detected (timer 0 arrives to 0000) switch 2 goes to Vref and the integrator runs down until a zero is detected on INT0; this causes the interrupt and the timer is halted. At this time the timer contains the converted data that remains in the TH0 and TL0 registers until a new conversion is started. Switch 1 allows the implementation of an autozero circuit, necessary to achieve the previously mentioned precision.