82801BA Datasheet, PDF (180/498 Pages) Intel Corporation – Intel 82801BA I/O Controller Hub 2 (ICH2) and Intel 82801BAM I/O Controller Hub 2 Mobile

Functional Description
Table 5-66 is a decision table illustrating the valid combinations of link pointer bits and the valid
actions taken when advancement criteria for a queued transfer descriptor are met. The column
headings for the link pointer fields are encoded, based on the following list:
QH
QHLP
QT
TD
TDLP Vf Q T
QE
QELP Vf Q T
Legends:
QH.LP = Queue Head Link Pointer (or Horizontal Link Pointer)
QE.LP = Queue Element Link Pointer (or Vertical Link Pointer)
TD.LP = TD Link Pointer
QH.Q = Q bit in QH
QH.T = T bit in QH
QE.Q = Q bit in QE
QE.T = T bit in QE
TD. Vf = Vf bit in TD
TD.Q = Q bit in TD
TD. T = T bit in TD
Table 5-66. USB Schedule List Traversal Decision Table
Q
Context
QH.Q
QH.T
QE.Q
QE.T
TD.Vf
TD.Q
TD.T
0
-
-
-
-
x
0
0
0
-
-
-
-
x
x
1
0
-
-
-
-
x
1
0
1
0
0
0
0
0
x
x
1
x
x
0
0
1
0
0
1
x
x
0
0
1
1
0
1
0
0
x
1
x
x
x
1
x
x
1
0
-
-
-
1
x
1
0
0
0
x
x
1
x
1
x
1
x
x
x
Description
• Not in Queue - execute TD.
• Use TD.LP to get next TD
• Not in Queue - execute TD. End of
Frame
• Not in Queue - execute TD.
• Use TD.LP to get next (QH+QE).
• Set Q Context to 1.
• In Queue. Use QE.LP to get TD.
• Execute TD. Update QE.LP with
TD.LP.
• Use QH.LP to get next TD.
• In Queue. Use QE.LP to get TD.
• Execute TD. Update QE.LP with
TD.LP.
• Use TD.LP to get next TD.
• In Queue. Use QE.LP to get TD.
• execute TD. Update QE.LP with
TD.LP.
• Use TD.LP to get next (QH+QE).
• In Queue. Empty queue.
• Use QH.LP to get next TD
• In Queue. Use QE.LP to get
(QH+QE)
• In Queue. Use QE.LP to get TD.
• execute TD. Update QE.LP with
TD.LP.
• End of Frame
• In Queue. Empty queue. End of
Frame
5-118
82801BA ICH2 and 82801BAM ICH2-M Datasheet