Test: Interfacing I/O Ports - Computer Science Engineering (CSE) MCQ

 Since joystick is an input device, it reads data from the external devices.

The output device transfers data from microprocessor to the external devices.

The input activity is similar to read operation and the output activity is similar to write operation.

IOWR (active low) operation means writing data to an output device and not an input device.

If the output port is to source large currents, the port lines must be buffered. So, the latch is used as it acts as good output port.

More current should not be sourced or sinked from data lines while reading to avoid loading.

 A tristate buffer is used as an input device to overcome loading.

The chip 74LS245 is a bidirectional buffer that contains 8 buffers and may be used as an 8-bit input port. But while using as an input device, only one direction is useful.

 If DIR is 1, then the direction is from A(inputs) to B(outputs).

In memory-mapped scheme, the devices are viewed as memory locations and are addressed likewise.