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.
![serial parallel converter circuit serial parallel converter circuit](https://s3.manualzz.com/store/data/020073220_1-0791831f3d547dfc47adc4f759b1522a-360x466.png)
![serial parallel converter circuit serial parallel converter circuit](https://m.media-amazon.com/images/I/51MVGkM1WJL._AC_.jpg)
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.
![serial parallel converter circuit serial parallel converter circuit](http://www.next.gr/uploads/8/Serial-to-Parallel%2BConverter%2BCircuit%2BDiagramw.gif)
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 interface circuit is also responsible for the format conversion that is essential for exchanging data between the processor and the I/O interface.The interface circuitry also generates the timing signals that synchronize the operation between the processor and the I/O device.The interface circuit also has address decoding circuitry which decodes the address over the address line to determine whether it is being addressed by the processor.The interface circuit also has the control register, the bits in the control register indicate the type of operation (read or write) requested by the processor to the I/O interface.The interface circuit also has a status register, the bits in the status register indicate the processor whether the I/O device is set for the transmission or not.The interface circuit has a data register that stores the data temporarily while the data is being exhanged between I/O and processor.We will discuss these ports in the section ahead.īut before discussing these ports let us take a brief outlook of what are the features of the I/O interface circuit. The port of the I/O interface can be a parallel port or a serial port. And this side of the I/O interface is referred to as the port. The other side of the interface circuit has the connections that are essential to transfer data between the I/O interface circuit and the I/O device. The data line is used to transfer the data between I/O and the processor. The control line is decoded to identify which kind of operation is requested by the processor.
![serial parallel converter circuit serial parallel converter circuit](https://www.allaboutcircuits.com/uploads/thumbnails/shift_path.png)
The address line is decoded by the interface circuit to determine if the processor has addressed this particular I/O device or not. Observe the figure below, we can easily see that the one end of the interface circuit is connected to the system bus line i.e., address line, data line, and control line. This mediator is referred to as an interface circuit. So, we need a mediator to make the computer communicate with the I/O modules. For example, the processing speed of the CPU is much higher than the other components of the computer such as keyboard, display, etc. We know that every component or module of the computer has its distinct capabilities and processing speed. Now the question is why do we require an 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.