MPC8536E-ANDROID Freescale Semiconductor, MPC8536E-ANDROID Datasheet - Page 1432

• Manufacturer Part Number: MPC8536E-ANDROID
• Description: HARDWARE/SOFTWARE ANDROID OS
• Manufacturer: Freescale Semiconductor
• Series: PowerQUICC ™r
• Type: MPUr

Specifications of MPC8536E-ANDROID

• Contents: Board
• For Use With/related Products: MPC8536
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Universal Serial Bus Interfaces
21.6.12.2.9 Rebalancing the Periodic Schedule
System software must occasionally adjust a periodic queue head's S-mask and C-mask fields during
operation. This need occurs when adjustments to the periodic schedule create a new bandwidth budget and
one or more queue head's are assigned new execution footprints (that is, new S-mask and C-mask values).
It is imperative that system software must not update these masks to new values in the midst of a split
transaction. In order to avoid any race conditions with the update, the host controller provides a simple
assist to system software. System software sets the Inactivate-on-next-Transaction (I) bit to signal the host
controller that it intends to update the S-mask and C-mask on this queue head. System software then waits
for the host controller to observe the I-bit is set and transitions the Active bit to a zero. The rules for how
and when the host controller clears the Active bit are:
System software must save transfer state before setting the I-bit. This is required so that it can correctly
determine what transfer progress (if any) occurred after the I-bit was set and the host controller executed
it's final bus-transaction and cleared the Active bit.
After system software has updated the S-mask and C-mask, it must then reactivate the queue head. Since
the Active bit and the I-bit cannot be updated with the same write, system software needs to use the
following algorithm to coherently re-activate a queue head that has been stopped using the I-bit.
Setting the Halted bit inhibits the host controller from attempting to advance the queue between the time
the I-bit is cleared and the Active bit is set.
21.6.12.3 Split Transaction Isochronous
Full-speed isochronous transfers are managed using the split-transaction protocol through a USB 2.0
transaction translator in a USB 2.0 hub. The host controller utilizes siTD data structure to support the
special requirements of isochronous split-transactions. This data structure uses the scheduling model of
isochronous TDs (see
model of iTDs) with the contiguous data feature provided by queue heads. This simple arrangement allows
a single isochronous scheduling model and adds the additional feature that all data received from the
endpoint (per split transaction) must land into a contiguous buffer.
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1. Set the Halted bit, then
2. Clear the I-bit, then
3. Set the Active bit and clear the Halted bit in the same write.
If the Active bit is cleared, no action is taken. The host controller does not attempt to advance the
queue when the I-bit is set.
If the Active bit is set and the SplitXState is DoStart (regardless of the value of S-mask), the host
controller simply clears the Active bit. The host controller is not required to write the transfer state
back to the current qTD. Note that if the S-mask indicates that a start-split is scheduled for the
current micro-frame, the host controller must not issue the start-split bus transaction; it must clear
the Active bit.
MPC8536E PowerQUICC III Integrated Processor Reference Manual, Rev. 1
Section 21.6.8, “Managing Isochronous Transfers Using iTDs,”
Freescale Semiconductor
for the operational