Data Acquisition Using INS8048

This application note describes techniques for interfacing National Semiconductor's ADC0833 serial I/O, and ADC0804 parallel I/O A/D converters to the INS8048 family of microprocessors. A hardware and software interface example is provided for each A/D, along with a brief theory of operation.

Since the INS8048 series microprocessors are single-chip, multiple I/O line, high speed devices designed as efficient controllers, the capacity to interface with analog peripherals is obvious. That the conversion be fast, inexpensive and easily expanded to accommodate a number of I/O devices is desirable.

The INS8048 is a self-contained, 8-bit processor in a 40-pin dual-in-line package. It contains its own system timing, control logic and memory. All parts contain RAM (64, 128, 256 bytes) and offer the option of on-board ROM (1k, 2k, 4k depending on part). It provides extensive bit-handling capabilities, 97 instructions, and offers easy expansion for I/O and memory. The ADC0833 A/D converter is an 8-bit successive-approximation device with serial I/O and conversion time of 25 ms.

This family of converters offers various configurations of multiplexed analog inputs which can be software programmed as single-ended, or as differential inputs, or both. Single-ended inputs are referenced to a common pin which is either referred to analog ground or to a fixed reference voltage. Like the INS8048 family, a single 5V power supply is all that is needed. The inputs will accept a 0V-5V range. No zero adjust is necessary. It is compatible with TTL and MOS at both input and output. The output can be selected as either MSB or LSB first.