Table of Contents
What are the three kinds of register in DMA controller?
The DMA controller has three registers as follows.
- Address register – It contains the address to specify the desired location in memory.
- Word count register – It contains the number of words to be transferred.
- Control register – It specifies the transfer mode.
What are the components of DMA controller?
A DMA controller can generate memory addresses and initiate memory read or write cycles. It contains several hardware registers that can be written and read by the CPU. These include a memory address register, a byte count register, and one or more control registers.
What are the two types of DMA?
Types of Device DMA
- Bus-Master DMA.
- Third-party DMA.
- First-party DMA.
What is Ds and Rs in DMA controller?
The register selects (RS) and device select (DS) lines are activated by addressing DMA controller and are perform read or write operations at the selected memory location. The acknowledge line is set by DMA when the system starts transfer operations. Data bus transfers data between external peripherals and memory.
What is IO processor?
The Input Output Processor is a specialized processor which loads and stores data into memory along with the execution of I/O instructions. It acts as an interface between system and devices. It involves a sequence of events to executing I/O operations and then store the results into the memory.
How DMA is different than I O processor?
DMA transfer is used for large data transfer. DMA transfers the data directly into the memory when the request is granted by the memory controller. To allow direct memory transfer(I/O), the CPU delays its memory access operation. So, DMA allows I/O devices to directly access memory with less intervention of the CPU.
What is third-party DMA?
Third-party DMA utilizes a system DMA engine resident on the main system board, which has several DMA channels available for use by devices. The device relies on the system’s DMA engine to perform the data transfers between the device and memory.
What is high impedance state in DMA?
High Impedance state means that the output is disconnected. The CPU activates the Bus Grant (BG) output to inform the external DMA that the Bus Request (BR) can now take control of the buses to conduct memory transfer without processor. When the DMA terminates the transfer, it disables the Bus Request (BR) line.
What is IOP in COA?
An input-output processor (IOP) is a processor with direct memory access capability. In this, the computer system is divided into a memory unit and number of processors. Each IOP controls and manage the input-output tasks.
How is IOP different from DMA?
In this approach, when a peripheral sends an interrupt signal to the CPU whenever it is ready to transfer data. This indicates that the I/O data transfer is initiated by the external I/O device….I/O Program Controlled Transfer vs DMA Transfer.
| S.No. | I/O Program Controlled Transfer | DMA Transfer |
|---|---|---|
| 2. | Data transfer speed is slow | Data transfer speed is fast. |
What is difference between DMA and IOP?
The I/O processor solves two problems: The job of input and output is assumed by the CPU. Although DMA does not require CPU for data exchange between peripherals and memory, it only reduces the burden of CPU. Because in DMA, the initialization of input and output is still done by CPU.
What is DMA Tutorialspoint?
DMA stands for Direct Memory Access. It allows the device to transfer the data directly to/from memory without any interference of the CPU. Using a DMA controller, the device requests the CPU to hold its data, address and control bus, so the device is free to transfer data directly to/from the memory.