Direct Memory Access : Différence entre versions

De Transcription | Bibliothèque patrimoniale numérique Mines ParisTech
Aller à : navigation, rechercher
(Page créée avec « <br>Without DMA, when the CPU is using programmed input/output, it is often totally occupied for [https://trevorjd.com/index.php/RNA_In_Reaction_To_Exterior_Occasions Mem... »)
 
m
 
Ligne 1 : Ligne 1 :
<br>Without DMA, when the CPU is using programmed input/output, it is often totally occupied for [https://trevorjd.com/index.php/RNA_In_Reaction_To_Exterior_Occasions Memory Wave System] all the duration of the read or write operation, and is thus unavailable to carry out other work. With DMA, the CPU first initiates the switch, then it does other operations while the transfer is in progress, and it finally receives an interrupt from the DMA controller (DMAC) when the operation is completed. This function is helpful at any time that the CPU can't sustain with the speed of data transfer, or when the CPU must perform work while waiting for a relatively gradual I/O data switch. Many hardware programs use DMA, including disk drive controllers, graphics playing cards, network playing cards and sound cards. DMA can be used for intra-chip information switch in some multi-core processors. Computers that have DMA channels can switch knowledge to and from units with much much less CPU overhead than computer systems with out DMA channels. Equally, a processing circuitry inside a multi-core processor can transfer information to and from its native memory without occupying its processor time, permitting computation and information switch to proceed in parallel.<br><br><br><br>DMA can also be used for "memory to memory" copying or moving of information within memory. DMA can offload costly memory operations, such as giant copies or scatter-collect operations, from the CPU to a devoted DMA engine. An implementation instance is the I/O Acceleration Technology. DMA is of curiosity in network-on-chip and in-memory computing architectures. Standard DMA, additionally called third-social gathering DMA, makes use of a DMA controller. A DMA controller can generate [http://juicy.iptime.org/board_XAde14/185952 Memory Wave System] addresses and initiate memory learn or write cycles. It accommodates a number of [https://www.tumblr.com/search/hardware%20registers hardware registers] that may be written and skim by the CPU. These include a memory deal with register, a byte count register, and a number of management registers. Relying on what features the DMA controller supplies, these control registers might specify some mixture of the supply, the destination, the course of the transfer (reading from the I/O gadget or writing to the I/O machine), the dimensions of the transfer unit, and/or the variety of bytes to transfer in one burst.<br><br><br><br>To carry out an enter, output or memory-to-memory operation, the host processor initializes the DMA controller with a depend of the number of words to transfer, and [https://elearnportal.science/wiki/Not_Like_Most_Of_The_Other_Entries Memory Wave] the memory deal with to make use of. The CPU then commands the peripheral system to initiate an information transfer. The DMA controller then offers addresses and read/write management traces to the system memory. Every time a byte of information is ready to be [https://www.deer-digest.com/?s=transferred transferred] between the peripheral device and memory, the DMA controller increments its internal address register till the full block of knowledge is transferred. Some examples of buses utilizing third-get together DMA are PATA, USB (before USB4), and SATA; nevertheless, their host controllers use bus mastering. In a bus mastering system, also known as a first-social gathering DMA system, the CPU and peripherals can every be granted control of the memory bus. The place a peripheral can turn out to be a bus grasp, it will possibly instantly write to system memory with out the involvement of the CPU, offering memory address and management alerts as required.<br><br><br><br>Some measures have to be supplied to put the processor right into a hold situation in order that bus contention does not happen. In burst mode, a complete block of information is transferred in a single contiguous sequence. As soon as the DMA controller is granted entry to the system bus by the CPU, it transfers all bytes of information in the information block earlier than releasing management of the system buses back to the CPU, but renders the CPU inactive for comparatively lengthy intervals of time. The mode is also called "Block Switch Mode". The cycle stealing mode is used in techniques by which the CPU should not be disabled for the length of time wanted for burst switch modes. In the cycle stealing mode, the DMA controller obtains access to the system bus the identical manner as in burst mode, [https://morphomics.science/wiki/User:DonnieHargreaves Memory Wave] utilizing BR (Bus Request) and BG (Bus Grant) signals, that are the two alerts controlling the interface between the CPU and the DMA controller. Nevertheless, in cycle stealing mode, after one unit of knowledge switch, the control of the system bus is deasserted to the CPU by way of BG.<br>
+
<br>With out DMA, when the CPU is using programmed enter/output, it is usually absolutely occupied for the whole duration of the read or write operation, and is thus unavailable to perform other work. With DMA, the CPU first initiates the switch, then it does different operations while the switch is in progress, and it finally receives an interrupt from the DMA controller (DMAC) when the operation is finished. This characteristic is helpful at any time that the CPU can not keep up with the speed of knowledge switch, or when the CPU must carry out work whereas waiting for a comparatively sluggish I/O knowledge switch. Many hardware systems use DMA, together with disk drive controllers, graphics cards, community cards and sound cards. DMA can be used for intra-chip information transfer in some multi-core processors. Computer systems which have DMA channels can transfer information to and from units with much much less CPU overhead than computers with out DMA channels. Equally, a processing circuitry inside a multi-core processor can switch knowledge to and from its native memory without occupying its processor time, permitting computation and data switch to proceed in parallel.<br><br><br><br>DMA may also be used for "memory to memory" copying or transferring of information inside memory. DMA can offload expensive memory operations, similar to large copies or scatter-gather operations, from the CPU to a dedicated DMA engine. An implementation example is the I/O Acceleration Expertise. DMA is of interest in network-on-chip and in-memory computing architectures. Commonplace DMA, also known as third-celebration DMA, makes use of a DMA controller. A DMA controller can generate memory addresses and initiate memory read or  [https://www.buyfags.moe/User:TerriCrick23821 MemoryWave Guide] write cycles. It incorporates several hardware registers that may be written and  [https://philmorrisphotography.com/galleries/street/peaky-blinders-1-of-1/ MemoryWave Guide] browse by the CPU. These include a memory tackle register, a byte rely register, and a number of management registers. Depending on what options the DMA controller provides, these control registers might specify some mixture of the supply, the vacation spot, the route of the switch (reading from the I/O system or writing to the I/O device), the dimensions of the transfer unit, and/or the variety of bytes to switch in one burst.<br><br><br><br>To perform an input, output or memory-to-memory operation, the host processor initializes the DMA controller with a count of the number of phrases to transfer, and the memory tackle to make use of. The CPU then commands the peripheral device to initiate a knowledge transfer. The DMA controller then provides addresses and browse/write control lines to the system memory. Every time a byte of knowledge is able to be transferred between the peripheral machine and memory, the DMA controller increments its inside deal with register until the full block of information is transferred. Some examples of buses using third-get together DMA are PATA, USB (before USB4), and SATA; nonetheless, their host controllers use bus mastering. In a bus mastering system, also called a primary-get together DMA system, the CPU and peripherals can each be granted management of the memory bus. Where a peripheral can change into a bus grasp, it could actually immediately write to system memory without the involvement of the CPU, offering memory tackle and management indicators as required.<br><br><br><br>Some measures should be provided to place the processor right into a hold situation so that bus contention does not occur. In burst mode, a complete block of information is transferred in one contiguous sequence. As soon as the DMA controller is granted access to the system bus by the CPU, it transfers all bytes of information in the data block before releasing control of the system buses back to the CPU, however renders the CPU inactive for comparatively lengthy periods of time. The mode can also be called "Block Transfer Mode". The cycle stealing mode is used in techniques wherein the CPU shouldn't be disabled for the size of time needed for burst switch modes. Within the cycle stealing mode, the DMA controller obtains access to the system bus the same approach as in burst mode, utilizing BR (Bus Request) and BG (Bus Grant) indicators, which are the two indicators controlling the interface between the CPU and the DMA controller. Nonetheless, in cycle stealing mode, after one unit of knowledge switch, the control of the system bus is deasserted to the CPU by way of BG.<br>

Version actuelle datée du 28 novembre 2025 à 17:13


With out DMA, when the CPU is using programmed enter/output, it is usually absolutely occupied for the whole duration of the read or write operation, and is thus unavailable to perform other work. With DMA, the CPU first initiates the switch, then it does different operations while the switch is in progress, and it finally receives an interrupt from the DMA controller (DMAC) when the operation is finished. This characteristic is helpful at any time that the CPU can not keep up with the speed of knowledge switch, or when the CPU must carry out work whereas waiting for a comparatively sluggish I/O knowledge switch. Many hardware systems use DMA, together with disk drive controllers, graphics cards, community cards and sound cards. DMA can be used for intra-chip information transfer in some multi-core processors. Computer systems which have DMA channels can transfer information to and from units with much much less CPU overhead than computers with out DMA channels. Equally, a processing circuitry inside a multi-core processor can switch knowledge to and from its native memory without occupying its processor time, permitting computation and data switch to proceed in parallel.



DMA may also be used for "memory to memory" copying or transferring of information inside memory. DMA can offload expensive memory operations, similar to large copies or scatter-gather operations, from the CPU to a dedicated DMA engine. An implementation example is the I/O Acceleration Expertise. DMA is of interest in network-on-chip and in-memory computing architectures. Commonplace DMA, also known as third-celebration DMA, makes use of a DMA controller. A DMA controller can generate memory addresses and initiate memory read or MemoryWave Guide write cycles. It incorporates several hardware registers that may be written and MemoryWave Guide browse by the CPU. These include a memory tackle register, a byte rely register, and a number of management registers. Depending on what options the DMA controller provides, these control registers might specify some mixture of the supply, the vacation spot, the route of the switch (reading from the I/O system or writing to the I/O device), the dimensions of the transfer unit, and/or the variety of bytes to switch in one burst.



To perform an input, output or memory-to-memory operation, the host processor initializes the DMA controller with a count of the number of phrases to transfer, and the memory tackle to make use of. The CPU then commands the peripheral device to initiate a knowledge transfer. The DMA controller then provides addresses and browse/write control lines to the system memory. Every time a byte of knowledge is able to be transferred between the peripheral machine and memory, the DMA controller increments its inside deal with register until the full block of information is transferred. Some examples of buses using third-get together DMA are PATA, USB (before USB4), and SATA; nonetheless, their host controllers use bus mastering. In a bus mastering system, also called a primary-get together DMA system, the CPU and peripherals can each be granted management of the memory bus. Where a peripheral can change into a bus grasp, it could actually immediately write to system memory without the involvement of the CPU, offering memory tackle and management indicators as required.



Some measures should be provided to place the processor right into a hold situation so that bus contention does not occur. In burst mode, a complete block of information is transferred in one contiguous sequence. As soon as the DMA controller is granted access to the system bus by the CPU, it transfers all bytes of information in the data block before releasing control of the system buses back to the CPU, however renders the CPU inactive for comparatively lengthy periods of time. The mode can also be called "Block Transfer Mode". The cycle stealing mode is used in techniques wherein the CPU shouldn't be disabled for the size of time needed for burst switch modes. Within the cycle stealing mode, the DMA controller obtains access to the system bus the same approach as in burst mode, utilizing BR (Bus Request) and BG (Bus Grant) indicators, which are the two indicators controlling the interface between the CPU and the DMA controller. Nonetheless, in cycle stealing mode, after one unit of knowledge switch, the control of the system bus is deasserted to the CPU by way of BG.