EP80579 Datasheet, PDF (969/1916 Pages) Intel Corporation – Intel® EP80579 Integrated Processor Product Line

Intel^® EP80579 Integrated Processor
Table 25-30. USB Schedule List Traversal Decision Table
Q
Context
0
0
0
1
1
1
1
1
1
1
1
1
QH.Q QH.T QE.Q QE.T TD.Vf TD.Q TD.T
Description
Not in Queue – execute TD.
-
-
-
-
x
0
0
Use TD.LP to get next TD
-
-
-
-
x
x
1
Not in Queue – execute TD. End of
Frame
Not in Queue - execute TD.
-
-
-
-
x
1
0 Use TD.LP to get next (QH+QE).
Set Q Context to 1.
In Queue. Use QE.LP to get TD.
0
0
0
0
0
x
x
execute TD. Update QE.LP with
TD.LP.
Use QH.LP to get next TD.
In Queue. Use QE.LP to get TD.
x
X
0
0
1
0
0
execute TD. Update QE.LP with
TD.LP.
Use TD.LP to get next TD.
In Queue. Use QE.LP to get TD.
x
X
0
0
1
1
0
execute TD. Update QE.LP with
TD.LP.
Use TD.LP to get next (QH+QE).
In Queue. Empty queue.
0
0
x
1
x
x
x
Use QH.LP to get next TD
x
X
1
0
-
-
- In Queue. Use QE.LP to get (QH+QE)
In Queue. Use QE.LP to get TD.
x
1
0
0
0
x
x
execute TD. Update QE.LP with
TD.LP.
End of Frame
x
1
x
1
x
x
x
In Queue. Empty queue. End of
Frame
In Queue. Use QE.LP to get TD.
1
0
0
0
0
x
x
execute TD. Update QE.LP with
TD.LP.
Use QH.LP to get next (QH+QE).
In Queue. Empty queue.
1
0
x
1
x
x
x
Use QH.LP to get next (QH+QE)
25.6
USB Buffer Management
The USB controller contains a 64 byte FIFO, which operate in a ping/pong fashion. This
buffer is not aligned to any memory boundary. Upon each new transfer descriptor (TD),
the buffer resets its pointer to the top.
When transmitting to a USB port, if the length field from the TD is greater than 32
bytes, meaning the internal FIFO boundary will be crossed, the host controller will read
both ping and pong together. When ping has been transferred to USB, and the total TD
length has not been fetched, the USB host controller will fetch another 32 bytes.
When receiving from a USB port, it is not known how many bytes will be received.
Therefore, the CMI will flush each buffer to memory as it becomes full.
August 2009
Order Number: 320066-003US
Intel^® EP80579 Integrated Processor Product Line Datasheet
969