What is the function of the Button on the PCD1.M1x5?

On Startup
The button next the extension memory is a HALT-button. If this button is pressed during startup, the PCD will not go in RUN-Mode. The PCD has to be restarted (power off/on) without pressing the button to bring the PCD back to RUN-Mode.

During RUN
This button can be used as input during RUN. With: “SYSRD K 8000 R_Switch” the status can be read into a diagnostic register. If Bit 0 (LSB) is high the button is not pressed. If Bit 0 is low, the button is pressed.

Since the button can only be used when the cover is missing we recommend using this button only for service functions.