Here is the clear description of Input – Output Processor:
An Input-Output Processor (IOP), also known as an I/O processor, is a specialized processor or microcontroller dedicated to handling input and output operations in a computer system.
• Its primary function is to manage data transfers between the central processing unit (CPU), memory, and various peripheral devices such as disk drives, network interfaces, keyboards, and displays.
Block Diagram of Input – Output Processor:
Here are some key aspects of Input-Output Processors:
‣ Interface with Peripherals:
IOPs serve as intermediaries between the CPU and various peripheral devices such as keyboards, mice, printers, storage devices, network interfaces, etc. They provide a standardized interface for communication between these devices and the CPU.
‣ Data Transfer:
IOPs facilitate the transfer of data between the CPU and peripherals. They manage data transfers efficiently, handling tasks like data buffering, error detection, and error correction to ensure reliable communication.
‣ Interrupt Handling:
IOPs handle interrupts generated by peripheral devices to signal events such as data arrival, completion of data transfer, or error conditions. Upon receiving an interrupt, the IOP suspends the CPU’s current task, processes the interrupt, and performs the necessary actions to handle the event.
‣ Device Control:
IOPs control the operation of peripheral devices by sending commands and receiving status information. They manage device initialization, configuration, and operation according to the requirements of the CPU and the applications running on it.
‣ I/O Addressing:
IOPs utilize I/O addressing mechanisms to access peripheral devices. They interpret I/O instructions issued by the CPU, translate them into appropriate signals or commands for the peripherals, and handle the data transfer between memory and devices.
‣ DMA (Direct Memory Access):
Many modern IOPs support DMA, a feature that enables data transfer between memory and peripherals without CPU intervention. DMA allows for faster data transfer rates and relieves the CPU from the burden of managing data transfers, improving overall system performance.
‣ Bus Interface:
IOPs connect to the system bus to communicate with the CPU and memory. They adhere to bus protocols and standards to ensure compatibility with the CPU and other system components.
‣ Parallelism and Pipelining:
Advanced IOPs may employ parallel processing and pipelining techniques to improve throughput and efficiency. Parallelism allows simultaneous processing of multiple I/O operations, while pipelining enables overlapping of different stages of I/O operations to reduce latency.
CPU-IOP Communication
- There is a communication channel between IOP and CPU to perform task which come under computer architecture. This channel explains the commands executed by IOP and CPU while performing some programs. The CPU do not executes the instructions but it assigns the task of initiating operations, the instructions are executed by IOP. I/O transfer is instructed by CPU. The IOP asks for CPU through interrupt.
Explanation:
• Communication channel between IOP and CPU Whenever CPU gets interrupt from IOP to access memory, it sends test path instruction to IOP. IOP executes and check for status, if the status given to CPU is OK, then CPU gives start instruction to IOP and gives it some control and get back to some another (or same) program, after that IOP is able to access memory for its program. Now IOP start controlling I/O transfer using DMA and create another status report as well. AS soon as this I/O transfer completes IOP once again send interrupt to CPU, CPU again request for status of IOP, IOP check status word from memory location and gives it to CPU. Now CPU check the correctness of status and continues with the same process.
IBM 370 I/O Channel:
The IBM 370 I/O Channel, also known as the Input/Output Channel, was a critical component in the IBM System/370 mainframe computers.
• It provided the interface between the central processing unit (CPU) and various input/output devices, facilitating data transfer between the CPU and these devices.
• The IBM 370 I/O Channel supported various types of devices, each with its own characteristics and functionalities.
Six Type of I/O Operations:
‣ write:
This operation involves transferring data from the computer’s memory to an external device or storage medium. For example, writing data to a disk or sending data over a network.
‣ Read:
The read operation is the opposite of write. It involves transferring data from an external device or storage medium into the computer’s memory. For example, reading data from a disk into memory.
‣ Read Backward:
This operation is less common but occasionally used in specialized scenarios. It involves reading data from an external device or storage medium in reverse order. This could be useful in certain data processing or analysis tasks.
‣ Control:
Control operations involve managing and coordinating I/O activities. This may include commands to start or stop data transfers, setting parameters for data transfer operations, or managing error handling during I/O operations.
‣ Sense:
Sensing operations involve gathering information about the status or condition of an I/O device or operation. This information could include error codes, device status flags, or other diagnostic information.
‣ Transfer in channel:
Transfer operations involve moving data between different parts of a computer system, such as between main memory and cache, between cache and processor registers, or between different levels of storage hierarchy (e.g., from disk to memory).
IBM-370 Channel Program Example:
Location of information in Memory for I/O Operations in the IBM 370:
Intel 8089 IOP:
The Intel 8089 is an Input/Output Processor (IOP) designed by Intel.
• It was intended to offload input/output (I/O) tasks from the CPU, thus improving overall system performance.
• The 8089 was primarily used in embedded systems and was part of the Intel MCS-86 microcontroller family.
Intel 8086/8089 Microcomputer system block diagram:
Location of information in memory for I/O operation in the intel 8086/8089 microcomputer system:
