How does the keyboard capture keystrokes? A microprocessor inside of the keyboard continually scans each key for when it is pressed and released. It then sends the interpreted ASCII value to the serial input port one bit at a time. The CPU monitors the keyboard keys and saves its ASCII value directly to RAM. When a key is pressed it's ASCII value is immediately sent to the input port. The keyboard places the key's $8-$bit ASCII value directly onto the system bus.