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Universal Serial Bus Interface
MCF5253 Reference Manual, Rev. 1
24-54
Freescale Semiconductor
24.8.4.3
siTD Transfer State
DWords 3–6 are used to manage the state of the transfer.
Table 24-46. Micro-frame Schedule Control
Bit
Name
Description
31–16
–
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) is
used to determine during which micro-frames the host controller should execute complete-split
transactions. 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 into
this bit field. If the FRINDEX register value indexes to a position where the µFrame C-Mask field is a
one, then this siTD is a candidate for transaction execution. There may be more than one bit in this
mask 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 to
determine during which micro-frames the host controller should execute start-split transactions. The
host controller uses the value of the three low-order bits of the FRINDEX register to index into this bit
field. If the FRINDEX register value indexes to a position where the µFrame S-mask field is a one, then
this siTD is a candidate for transaction execution. An all zeros value in this field, in combination with
existing periodic frame list has undefined results.
Table 24-47. siTD Transfer Status and Control
Bit
Name
Description
31
ioc
Interrupt On Complete
0 Do not interrupt when transaction is complete.
1 Do interrupt when transaction is complete. When the host controller determines that the split
transaction 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 the
CurrentOffset field to construct a data buffer pointer.
0 Selects Page 0 pointer
1 Selects Page 1 pointer
The host controller is not required to write this field back when the siTD is retired (Active bit
transitioned from a one to a zero).
29–26
–
Reserved. This field reserved for future use and should be cleared.
25–16
Total Bytes to
Transfer
This field is initialized by the software to the total number of bytes expected in this transfer. Maximum
value is 1023 (3FFh)
15–8 µFrame
C-prog-mask
Split complete progress mask. This field is used by the host controller to record which
split-completes have been executed.
Содержание MCF5253
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