I am interfacing Epson LX-300 printer with 8051 using the parallel port. I have used 8 data lines, i strobe and 1 busy line for this purpose. I am able to send data to printer and it works fine. The issue I am facing is the following:
The printer is powered on and the controller is off. Now if the controller is switched on, the printer first prints some garbage value. After this all the data printed is correct. I am not able to make out why the printer is printing garbage value at system startup
The standard rule about designing hardware: what state will the pins take when the unit isn't powered? What state will they take when the processor is powered but in reset state? Is these states compatible with connected hardware? Any need for pull-up? Any need for pull-down? Any need for inverting some signal?
The goal is obviously to make sure that all signals will stay in their idle state when the device isn't powered or is reset, to avoid creating any glitches.