Universal Serial Bus Interface
MCF5253 Reference Manual, Rev. 1
24-48
Freescale Semiconductor
Frame List Link pointers always reference memory objects that are 32-byte aligned. The referenced object
may be an isochronous transfer descriptor for high-speed devices, a split-transaction isochronous transfer
descriptor (for full-speed isochronous endpoints), or a queue head (used to support high-, full- and
low-speed interrupt). The system software should not place non-periodic schedule items into the periodic
schedule. The least significant bits in a frame list pointer are used to key the host controller as to the type
of object the pointer is referencing.
The least significant bit is the T-Bit (bit 0). When this bit is set, the host controller will never use the value
of the frame list pointer as a physical memory pointer. The Typ field is used to indicate the exact type of
data structure being referenced by this pointer. The value encodings for the Typ field are given in
.
24.8.2
Asynchronous List Queue Head Pointer
The Asynchronous Transfer List (based at the ASYNCLISTADDR register) is where all the control and
bulk transfers are managed. Host controllers use this list only when it reaches the end of the periodic list,
the periodic list is disabled, or the periodic list is empty.
Figure 24-37. Asynchronous Schedule Organization
The Asynchronous list is a simple circular list of queue heads. The ASYNCLISTADDR register is simply
pointer to the next queue head. This implements a pure round-robin service for all queue heads linked into
the asynchronous list.
31
5
4
3
2
1
0
Frame List Link Pointer
00
Typ
T
Figure 24-36. Frame List Link Pointer Format
Table 24-37. Typ Field Encodings
Typ
Description
00 Isochronous
Transfer
Descriptor
01 Queue
Head
10
Split Transaction Isochronous Transfer Descriptor
11
Frame Span Traversal Node.
AsyncListAddr
Operational
Registers
Bulk/Control Queue Heads
H
Summary of Contents for MCF5253
Page 1: ...Document Number MCF5253RM Rev 1 08 2008 MCF5253 Reference Manual...
Page 26: ...MCF5253 Reference Manual Rev 1 xxvi Freescale Semiconductor...
Page 32: ...MCF5253 Reference Manual Rev 1 xxxii Freescale Semiconductor...
Page 46: ...MCF5253 Introduction MCF5253 Reference Manual Rev 1 1 14 Freescale Semiconductor...
Page 62: ...Signal Description MCF5253 Reference Manual Rev 1 2 16 Freescale Semiconductor...
Page 98: ...Instruction Cache MCF5253 Reference Manual Rev 1 5 10 Freescale Semiconductor...
Page 104: ...Static RAM SRAM MCF5253 Reference Manual Rev 1 6 6 Freescale Semiconductor...
Page 128: ...Synchronous DRAM Controller Module MCF5253 Reference Manual Rev 1 7 24 Freescale Semiconductor...
Page 144: ...Bus Operation MCF5253 Reference Manual Rev 1 8 16 Freescale Semiconductor...
Page 176: ...System Integration Module SIM MCF5253 Reference Manual Rev 1 9 32 Freescale Semiconductor...
Page 198: ...Analog to Digital Converter ADC MCF5253 Reference Manual Rev 1 12 6 Freescale Semiconductor...
Page 246: ...DMA Controller MCF5253 Reference Manual Rev 1 14 18 Freescale Semiconductor...
Page 282: ...UART Modules MCF5253 Reference Manual Rev 1 15 36 Freescale Semiconductor...
Page 344: ...Audio Interface Module AIM MCF5253 Reference Manual Rev 1 17 46 Freescale Semiconductor...
Page 362: ...I2 C Modules MCF5253 Reference Manual Rev 1 18 18 Freescale Semiconductor...
Page 370: ...Boot ROM MCF5253 Reference Manual Rev 1 19 8 Freescale Semiconductor...