Observe the output interface shown in the figure below that connects the display and processor. The bus connecting processor and interface has one more control line i.e., R/W which is set to one for reading operation. Whenever the processor is ready to accept the data, it activates its master-ready line and whenever the interface is ready with the data to transmit it to the processor it activates its slave-ready line. So, the way they alert each other is using the master ready line and the slave ready line. Here the input interface is connected to the processor using an asynchronous bus. Once the processor reads the data from KBD_DATA register the KIN flag is again set to 0. Which causes the processor to read the data from KBD_DATA. Now, when the data is loaded into the KBD_DATA register the KIN status flag present in the KBD_STATUS register is set to1.
SERIAL PARALLEL CONVERTER CIRCUIT CODE
So, when the valid bit is 1 the ASCII code of the corresponding character is loaded to the KBD_DATA register of the input interface circuit. This valid bit changes its status from 0 to 1 when the key is pressed. The encoder then outputs one byte of data that presents the character encoded by the encoder along with one valid bit. This signal is encoded by the encoder to convert it into ASCII code for the corresponding character pressed at the keyboard. Now, whenever the key is tapped on the keyboard an electrical connection is established that generates an electrical signal. Observe the parallel input port that connects the keyboard to the processor. Here multiple bits are transferred at once. First, we will study an input device i.e., a keyboard that has an 8-bit input port, and then an output device i.e., a display that has an 8-bit output port. To understand the interface circuit with a parallel port we will take the example of two I/O devices.
SERIAL PARALLEL CONVERTER CIRCUIT SERIAL
Now, let us learn about the parallel port and the serial port of the I/O interface circuit.
The I/O interface circuit is circuitry that is designed to link the I/O devices to the processor. We will also discuss two variants of interface circuit design i.e., parallel interface and the serial interface.
In this context, we will discuss the I/O interface circuit in more detail along with its entire functioning.