
384 The Essential Guide to Serial ATA and SATA Express
Host to Device FIS Transmission
When transferring a FIS from the host to a device (disk) through a PM (see Figure 9.4), the
1. Host places PM port field into FIS
2. Host transmits FIS to PM
3. PM examines PM field for Port number
4. PM transmits FIS to device
Example of Primitive Protocol
When a Port Multiplier forwards a FIS, all it needs is the first Dword to determine which device port
it will forward the FIS through. This forwarding process can start immediately or the PM could have
buffers to capture either a portion or all of the FIS prior to routing. Figure 9.5 shows how the ...