Human Humalyzer 2000 - System Control

Rev. B 5
thermal printer, the printer PCB, and metal supports, is mounted to the rear dress panel and is
connected to the interface PCB via a 14-pin DIP cable.
System Control
The instrument is based on the 8 bit Z80 microprocessor. The software is permanently stored in a
27256 EPROM. A battery-backed non-volatile RAM (random access memory) chip (MK48T08)
incorporating a real-time clock is used store data such as calibration, test setups, samples, and
also maintains the date and time. A static RAM chip (6264) is used for temporary storage.
Almost all digital I/O is accomplished with an 8255 Programmable Peripheral Interface. Time
intervals and pulse widths are measured using the counter channels of an 8254 programmable
timer.