FUJITSU MHW2120BS - Manual (Page 88)

Interface
5.2 Logical Interface
The host system and the device communicate with each other by sending and
receiving serial data.
The host and the device have several dedicated communication layers between
them. These layers have different functions, enabling communication between the
different levels of layers within the host or device and between layers at the same
level that link the host and device.
Figure 5.3 is a conceptual diagram of the communication layers.
Host:
Software control
Buffer Memory
DMA engine(s)
Host located layers
Physical Layer
Link Layer
Transport Layer
Device located layers
Physical Layer
Link Layer
Transport Layer
Device:
Software control
Buffer memory
DMA engine(s)
Application
layer 4
Transport
layer 3
Link
layer 2
Physical
layer 1
Shadow Block Register Block Register
Figure 5.3 Conceptual diagram of communication layers
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