Information
Universal Serial Bus Interface
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
Freescale Semiconductor 13-125
Figure 13-61 shows the Endpoint Queue Head structure.
13.7.1.1 Endpoint Capabilities/Characteristics
This DWord specifies static information about the endpoint, in other words, this information does not
change over the lifetime of the endpoint. Device controller software should not attempt to modify this
information while the corresponding endpoint is enabled.
Table 13-75 describes the endpoint capabilities and characteristics fields.
313029282726252423222120191817161514131211109 8 76543 2 1 0 offset
Mult zlt 00 Maximum Packet Length ios 000_0000_0000_0000 0x00
Current dTD Pointer
1
1
Device controller read/write; all others read-only.
0_0000 0x04
Next dTD Pointer
1
0000 T
1
0x08
2
2
Offsets 0x08 through 0x20 contain the transfer overlay.
0 Total Bytes
1
ioc
1
000 MultO
1
00 Status
1
0x0C
2
Buffer Pointer (Page 0)
1
Current Offset
1
0x10
2
Buffer Pointer (Page 1)
1
Reserved 0x14
2
Buffer Pointer (Page 2)
1
Reserved 0x18
2
Buffer Pointer (Page 3)
1
Reserved 0x1C
2
Buffer Pointer (Page 4)
1
Reserved 0x20
2
Reserved 0x24
Setup Buffer Bytes 3–0
1
0x28
Setup Buffer Bytes 7–4
1
0x2C
Figure 13-61. Endpoint Queue Head Layout
Table 13-75. Endpoint Capabilities/Characteristics
Bits Name Description
31–30 Mult Mult. This field is used to indicate the number of packets executed per transaction description as given by
the following:
00 - Execute N Transactions as demonstrated by the USB variable length packet protocol where N is
computed using the Maximum Packet Length (dQH) and the Total Bytes field (dTD)
01 Execute 1 Transaction.
10 Execute 2 Transactions.
11 Execute 3 Transactions.
Note: Non-ISO endpoints must set Mult = 00.
Note: ISO endpoints must set Mult = 01, 10, or 11 as needed.
29 zlt Zero length termination select. This bit is used to indicate when a zero length packet is used to terminate
transfers where to total transfer length is a multiple. This bit is not relevant for Isochronous transfers.
0 Enable zero length packet to terminate transfers equal to a multiple of the Maximum Packet Length.
(default).
1 Disable the zero length packet on transfers that are equal in length to a multiple Maximum Packet
Length.