WEARABLE TECH AND BIOMETRICS
happen in the background. For example, on Arm architectures, a DMA module can operate during LP2 (sleep) or LP3 (run) modes. This can give a distinct advantage in applications that require extended battery life, such as wearable sensor hubs and smart watches.
Advantages and Drawbacks DMA is useful in many digital systems and sometimes it is even required to manage used in network cards, graphics cards and said, incorporating DMA into a design does have some trade-offs.
Figure 1. An architectural diagram of burst DMA during DMA operations.
Type of DMA
Pros Fastest type of DMA Cons
Relatively long periods
Transparent DMA Table 3. Summary of DMA types and their pros/cons
Bus Access and CPU Cycles While DMA controllers can be incredibly effective at conserving power or speeding up embedded systems, their implementation is not heavily standardised. There are multiple schemes for making sure that internal bus access is not granted simultaneously with is primarily to avoid concurrent access to the same memory locations, which can lead to cache incoherency and logical errors. A single employ one of these schemes, since different required to use each of them. The bus access schemes used by most DMA controllers are burst, cycle-stealing and transparent DMA. Transparent DMA can only execute a single operation at a time, but it must also wait for the processor to execute instructions in which it yields access to the desired data or address buses. Extra logic is required to verify this access restriction and this type of DMA is generally the slowest. Transparent DMA may be advantageous in applications where one has extra processing to do that does not require access to the memory buses. The advantage in this case would be processor does not have to stop operating completely.
computational strain on the processor, causing longer periods in active power modes and slow response times.
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Managing input can put a lot of unnecessary
bursts, where the DMA controller sends as much data to the destination buffer as the buffer can hold. The DMA controller blocks move a large chunk of memory and then DMA is generally considered the fastest type. cycle-stealing DMA takes a cue from the of executing one operation at a time, it is generally slower than burst DMA.
Example of a Burst DMA Architecture
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An example of a burst DMA controller can be found on the MAX32660 (see Figure 4). and the lower path represents control/
Figure 2. Cycle-stealing DMA during DMA operations occurs between two CPU cycles. MAY 2022 | ELECTRONICS TODAY 39
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