Switching interface circuit in timing query mode

In the timed query mode, the CPU periodically reads the switch status at a specified time. This method cannot
accurately reflect the changing time of the switch status, and the error is related to the reading cycle. The interface using the timing query method is very simple. If you read from the data bus, you only
need to add the bus buffer. The picture shows the interface circuit using 74LS244 . For microcontrollers, the switching input signal can also be directly
connected to the I/O interface without adding interface components.