5.2 Logical 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.
|
|
|
|
|
|
|
|
|
|
|
| Application |
|
|
|
|
|
|
|
|
| ||||||||||||||||
|
| Host: |
|
|
|
|
|
|
|
|
|
| Device: | ||||||||||||||||||||||||
|
|
|
|
|
|
|
|
| layer 4 |
|
|
|
|
| |||||||||||||||||||||||
|
| Software control |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| Software control | ||||||||
|
| Buffer Memory |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| Buffer memory | ||||||||
|
| DMA engine(s) |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| DMA engine(s) | ||||||||
|
|
|
|
|
|
|
|
|
|
|
|
| Transport |
|
|
|
|
|
|
|
|
| |||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||||||||||||
|
| Shadow Block Register |
|
|
|
|
|
|
|
|
|
| layer 3 |
|
|
|
|
| Block Register |
| |||||||||||||||||
|
| Transport Layer |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| Transport Layer |
| ||||||
|
|
|
|
|
|
|
|
|
|
| Link |
|
|
|
|
| |||||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||||||||
|
| Link Layer |
|
|
|
|
|
|
|
| layer 2 |
|
|
|
|
| Link Layer | ||||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||||
|
|
|
|
| Physical |
|
|
| |||||||||||||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| layer 1 |
|
|
|
|
|
|
|
|
| |||||||||||||
|
| Physical Layer |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| Physical Layer | ||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
| |||||||||||||||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Host located layers | Device located layers |
Figure 5.3 Conceptual diagram of communication layers