![](http://datasheet.mmic.net.cn/380000/-PD98501_datasheet_16745028/-PD98501_415.png)
CHAPTER 6 USB CONTROLLER
Preliminary User’s Manual S14767EJ1V0UM00
415
Figure 6-6. Configuration of Send Packet Descriptors
-Tx Packet Directory
Directory Address
-Tx Link Pointer
Reserved
31
0
0
Buffer Descriptor N
Buffer Descriptor 4
Buffer Descriptor 3
Buffer Descriptor 2
Buffer Descriptor 1
Buffer Descriptor 0
Link Pointer
-Tx Buffer Descriptor
31
0
16 15
Buffer Address
L
Size
-Tx Packet Descriptor
31
0
16 15
Directory Address
|
1
1
0
1
Reserved
30
29
30
29
28
31
30
29
0
0
Reserved
EPN
Reserved
B
9
8
Tx Packet Descriptor:
Maintains the data in the Tx Packet.
Bit 31 to bit 29 are set to 110.
EPN indicates the number of the EndPoint that is to send a packet.
Bit0 indicates whether it is possible to write the next command..
The "Directory Address" field indicates the start address of the send packet directory.
This is the send packet directory. It is configured by bundling together the buffer
descriptor and the link pointer. A single send Buffer Directory can accommodate up to
255 buffer descriptors.
This is the send buffer descriptor. It maintains the data in the receive buffer.
When Bit31 (Last bit) is active, the Buffer Descriptor indicates the last buffer in a packet.
Bit30 is used to discriminate between the Buffer Descriptor and Link Pointer. When set to
1, this bit indicates the Buffer Descriptor.
The "Size" field indicates the buffer size. As the buffer size, a value between 1 and 64K
bytes can be set. The "Buffer Address" field indicates the head address of the buffer.
This is the link pointer. It points to the next packet directory.
Bit31 is usually set to 0.
Tx Packet Directory:
Tx Buffer Descriptor:
Tx Link Pointer: