基于OHCI的USB主机 —— OHCI(ED结构)

简介:
ED数据结构,定义如下:
typedef   struct  _AT91S_UHP_ED {

     volatile   unsigned   int   Control ;

     volatile   unsigned   int   TailP ;

     volatile   unsigned   int   HeadP ;

     volatile   unsigned   int   NextEd ;

AT91S_UHP_ED , * AT91PS_UHP_ED ;

 
Endpoint Descriptor Format
An Endpoint Descriptor (ED) is a 16-byte, memory resident structure that must be aligned to a 16-byte boundary.  The Host Controller traverses lists of EDs and if there are TDs linked to an ED, the Host Controller  performs the indicated transfer. 
 
3
 
 
 
2
 
 
 
 
 
 
 
 
 
1
1
1
1
1
1
1
 
0
0
0
0
0
0
0
0
 
1
 
 
 
6
 
 
 
 
 
 
 
 
 
6
5
4
3
2
1
0
 
7
6
5
4
3
2
1
0
Dword 0
MPS
F
K
S
D
EN
FA
Dword 1
TD Queue Tail Pointer (TailP)
Dword 2
TD Queue Head Pointer (HeadP)
0
C
H
Dword 3
Next Endpoint Descriptor (NextED)
Notes :
1.        Fields containing ‘—’ are not interpreted or modified by the Host Controller and are available for use by the Host Controller Driver for any purpose.
2.        Fields containing ‘0’ must be written to 0 by the Host Controller Driver before queued for Host Controller processing.  If Host Controller has write access to the field, it will always write the field to 0.





本文转自 tywali 51CTO博客,原文链接:http://blog.51cto.com/lancelot/240819,如需转载请自行联系原作者
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