Periodic Isochronous—Do-Start-Split - Freescale Semiconductor MPC8313E Family Reference Manual

transaction state machine is used to manage the split-transaction protocol sequence. The host controller
uses the fields defined in
Transfers," plus the variable cMicroFrameBit defined in
State Machine for Interrupt,"
illustrates the state machine for managing an siTD through an isochronous split transaction. Bold, dotted
circles denote the state of the Active bit in the Status field of a siTD. The Bold, dotted arcs denote the
transitions between these states. Solid circles denote the states of the split transaction state machine and
the solid arcs denote the transitions between these states. Dotted arcs and boxes reference actions that take
place either as a result of a transition or from being in a state.
Not Active
Active = 0b
OUT Split
Active = 0b
Transaction
Complete
IN Split
Transaction
Complete
Advance data buffer state
Figure 16-59. Split Transaction State Machine for Isochronous
16.6.12.3.4 Periodic Isochronous—Do-Start-Split
Isochronous split transaction OUTs use only this state. An siTD for a split-transaction isochronous IN is
either initialized to this state, or the siTD transitions to this state from Do Complete Split when a case 2a
(IN) or 2b scheduling boundary isochronous split-transaction completes.
Each time the host controller reaches an active siTD in this state, it checks the siTD[S-mask] against
cMicroFrameBit. If there is a one in the appropriate position, the siTD executes a start-split transaction.
By definition, the host controller cannot reach an siTD at the wrong time. If the I/O field indicates an IN,
then the start-split transaction includes only the extended token plus the full-speed token. Software must
initialize the siTD[Total Bytes To Transfer] field to the number of bytes expected. This is usually the
maximum packet size for the full-speed endpoint. The host controller exits this state when the start-split
transaction is complete.
MPC8313E PowerQUICC II Pro Integrated Processor Family Reference Manual, Rev. 3
Freescale Semiconductor
Section 16.6.12.3.2, "Tracking Split Transaction Progress for Isochronous
to track the progress of an isochronous split transaction.
Active = 1b
siTD.S-mask & cMicroFrameBit
.and.
direction .eq. OUT
Do Start
Split
case 2(a,b)
Active
siTD x-1 complete
Do
Complete
Split
MDATA
NYET
.and.
Not Last
Section 16.6.12.2.5, "Split Transaction Execution
issue start-split transaction
siTD.C-mask & cMicroFrameBit
.and.
direction .eq. IN
siTD.C-mask & cMicroFrameBit
.and.
checkPreviousBit(C-prog-mask, C-mask, cMicroFrameBit)
Universal Serial Bus Interface
Figure 16-59
issue complete-split
transaction
16-113