In this mode, data transfer is initiated by instructions written in a computer program.
Difference between programmed and interrupt-initiated I/O:
Programmed I/O interrupt Initiated I/O
Its module is treated as a slow module. Its module is faster than the programmed I/O module.
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Difference between programmed and interrupt-initiated I/O
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Interrupt-driven I/O is an approach to transfer data between “memory” and “I/O devices” through the “processor”. The other two techniques for doing this are programmed I/O and direct memory access (DMA). Interrupt-driven I/O involves the use of interrupts to pass data between I/O and memory.
When the I/O operation is complete, the I/O module interrupts the processor and notifies it that the operation is complete. Its module is faster than the programmed I/O module. The processor actually starts the I/O device and instructs it to generate and send an interrupt signal when the operation is complete.
There is no query. The acronym “PIO” has always stood for “Programmed Input/Output”.
Programmed input-output (also programmable input/output, programmed input/output, programmed I/O, PIO) is a method of data transfer via input/output (I/O) between a central processing unit (CPU ) and a peripheral device such as a network adapter or a parallel ATA storage device.
The problem with programmed I/O is that the processor has to wait a long time for that I/O module to get ready to receive or transmit more data. The processor must keep polling the status of the input/output module while waiting.
With interrupt-driven data transfer, the CPU is interrupted whenever the I/O device is ready for data transfer. In the ISR, the CPU performs the data transfer. This method is better than polling because the CPU doesn’t have to waste time checking the status of the I/O device.
DMA is an acronym for Direct Memory Access. DMA is a method of transferring data between main memory and peripheral devices. The hardware unit that controls DMA transfers is a DMA controller. The DMA controller transfers data to and from memory without processor involvement.
The main difference between interrupt and polling is that interrupting is the device telling the CPU that it needs attention whereas polling has the CPU continuously checking the status of the devices to see if they need attention.
The term programmed I/O can refer to either memory-mapped I/O (MMIO) or port-mapped I/O (PMIO). PMIO refers to transfers that use a special address space outside of normal memory, typically accessed with dedicated instructions such as IN and OUT in x86 architectures.
We have three different transfer modes: programmed I/O, interrupt-initiated I/O, and Direct Memory Access (DMA). Programmed I/O and interrupt-initiated I/O are transfer modes that involve the CPU for data transfer.
Busy-wait I/O may be the cheapest implementation for systems that only need to do one thing at a time. Interrupt-driven I/O is preferable when the I/O is time-sensitive and in a multi-threaded process/system.
If you ask about data transfer methods, DMA (direct memory access) is done without processor involvement using an external controller. Interruption requires the processor to temporarily stop its work to transfer some data by reading (or writing) it directly to or from a memory location.
An Interrupt Service Routine (ISR) is a software routine called by the hardware in response to an interrupt. ISR examines an interrupt and determines how to handle it, executes the handling, and then returns a logical interrupt value. If no further handling is required, the ISR notifies the kernel with a return value.