Universal Serial Bus InterfaceMCF5253 Reference Manual, Rev. 124-54 Freescale Semiconductor24.8.4.3 siTD Transfer StateDWords 3–6 are used to manage the state of the transfer.Table 24-46. Micro-frame Schedule ControlBit Name Description31–16 – Reserved. This field reserved for future use. It should be cleared.15–8 μFrame C-mask Split Completion Mask. This field (along with the Active and SplitX- state fields in the Status byte) isused to determine during which micro-frames the host controller should execute complete-splittransactions. When the criteria for using this field is met, an all zeros value has undefined behavior.The host controller uses the value of the three low-order bits of the FRINDEX register to index intothis bit field. If the FRINDEX register value indexes to a position where the μFrame C-Mask field is aone, then this siTD is a candidate for transaction execution. There may be more than one bit in thismask set.7–0 μFrame S-mask Split Start Mask. This field (along with the Active and SplitX-state fields in the Status byte) is used todetermine during which micro-frames the host controller should execute start-split transactions. Thehost controller uses the value of the three low-order bits of the FRINDEX register to index into this bitfield. If the FRINDEX register value indexes to a position where the μFrame S-mask field is a one, thenthis siTD is a candidate for transaction execution. An all zeros value in this field, in combination withexisting periodic frame list has undefined results.Table 24-47. siTD Transfer Status and ControlBit Name Description31 ioc Interrupt On Complete0 Do not interrupt when transaction is complete.1 Do interrupt when transaction is complete. When the host controller determines that the splittransaction has completed, it will assert a hardware interrupt at the next interrupt threshold.30 P Page Select. Used to indicate which data page pointer should be concatenated with theCurrentOffset field to construct a data buffer pointer.0 Selects Page 0 pointer1 Selects Page 1 pointerThe host controller is not required to write this field back when the siTD is retired (Active bittransitioned from a one to a zero).29–26 – Reserved. This field reserved for future use and should be cleared.25–16 Total Bytes toTransferThis field is initialized by the software to the total number of bytes expected in this transfer. Maximumvalue is 1023 (3FFh)15–8 μFrameC-prog-maskSplit complete progress mask. This field is used by the host controller to record whichsplit-completes have been executed.
