Design Flub Fixed
Pinout diagram of Zilog Z80 microprocessor Back around 1989, I received a request to fix an infusion pump, a device that allows medical staff to pump very small, and precise, amounts of fluids and medicines into patients. I was told it would turn on but wouldn't start pumping. The display showed rubbish and pushing buttons didn't produce any response. I opened the thing and quickly discovered a Z80 microprocessor, a computer chip that I had been studying for some time with the intention of building my own computer. I was very familiar with it. From the description of the problem, it seemed as if the unit was not starting up properly. Opening the unit and checking pin 26 (the RESET pin), I found...nothing, the pin was floating (unconnected to anything). The chip needs the RESET pin to be held at 0 volts for about a split-second after power-on to start the program at the beginning. If the chip is not reset, the program may start at a random line and the unit will likely