What is the Interrupt I/O Process?

Introduction

One important computer technology that improves input/output (I/O) efficiency is interrupt I/O. An interrupt signal is generated when a device, like a disc drive or keyboard, has data that is ready to be processed. This interrupts the task that the CPU is working on. After that, the CPU stops processing data, hands off control to an interrupt handler, and resumes processing the incoming data. Because it is asynchronous, the CPU can work on other tasks while waiting for I/O to finish, which improves system performance and responsiveness.

Configuration of I/O

Serial information is sent and received by the terminals. Eight bits of alphanumeric code make up each segment of serial data, with the leftmost bit always being 0. The serial data that was previously in the input register is received by the input register INPR. The output register, or OUTR, is where the printer's serial data can be stored. These two registers communicate in a serial structure via a communication link and in tandem with the Accumulator (AC).

The figure displays the input/output arrangement. Serial data is obtained from the keyboard by the transmitter interface and sent to INPR. Data is obtained from OUTR and serially transferred to the printer by the receiver interface.

There are eight bits in the input/output registers. An input flag with one bit, the FGI is a control flip-flop. After the device receives the data, the flag bit is cleared to 0 and is set to 1 when fresh data enters the input device.

The matching alphanumeric code is moved to INPR, and the input flag FGI is set to 0 when a key is pushed on the keyboard. Since the flag is set, it is not possible to alter the data in INPR. When the flag bit is set to 1, INPR data is simultaneously sent into AC, and the FGI is cleared to 0. This is how the device checks the flag bit.

The input register INPR and the output register OUTR carry out comparable functions.

The OUTR's data flow is the opposite of the INPR's. The output flag FGO was, therefore, initially set to 1. The device clears the FGO to 0 and sends AC data to OUTR in parallel when the flag bit is set to 1. When the FGO is zero, the output device prints a character, indicating that no more data can be loaded into OUTR.

Input Register

Eight bits make up the INPR input register, which affects alphanumeric input data. Manage the flip-flop One-bit input flag or FGI. The flag bit is set to 1 when the input device has new data available. The data is cleared to 0 when the device accepts it. The flag is necessary in order to synchronize the time rate disparity between the input device and the computer.

The process for transferring data is as follows:

• The input flag, FGI, is set to zero. When a user clicks any key on the keyboard, an 8-bit alphanumeric code is entered into INPR, and the input flag FGI is set to 1.
• The device tests the flag bit. If the bit is 1, the FGI is cleared to 0. Otherwise, the data from INPR is sent to AC.
• Another key can be used to enter INPR and submit fresh data once the flag has been removed.

Output Register

Since the input register INPR and the output register OUTR function similarly, the direction of data flow control is inverted.

The data transfer process goes like this:

• The output flag FGO has a value of 1.
• The device tests the flag bit. When the bit is set to 1, AC data is shared to OUTR and FGO is simultaneously cleared to 0.
• After receiving the coded 8-bit data, the output device produces the matched character.
• When this process is finished, the output device sets the FGO to 1.

Conclusion

Interrupt input/output, a fundamental component of computing, enables efficient handling of data from external devices. Improved system responsiveness and multitasking are achieved by interrupting I/O, which allows the CPU to respond asynchronously to external events. This technique, which keeps the CPU from becoming idle during I/O operations, is crucial for preserving optimal resource utilization in a range of computing scenarios.