Freescale Semiconductor MPC5200B ユーザーズマニュアル
MPC5200B Users Guide, Rev. 1
12-2
Freescale Semiconductor
Host Controller Interface
•
Bulk Transfers—Non-periodic data transfers used to communicate large amounts of information between client software and the
USB device.
USB device.
In OpenHCI the data transfer types are classified into two categories: periodic and nonperiodic. Periodic transfers are interrupt and
isochronous since they are scheduled to run at periodic intervals. Non-periodic transfers are control and bulk since they are not scheduled to
run at any specific time, but rather on a time-available basis.
isochronous since they are scheduled to run at periodic intervals. Non-periodic transfers are control and bulk since they are not scheduled to
run at any specific time, but rather on a time-available basis.
12.3
Host Controller Interface
12.3.1
Communication Channels
There are two communication channels between the HC and HCD.
1.
The first channel uses a set of operational registers located on the HC. The HC is the target for all communication on this channel.
The operational registers contain control, status, and list pointer registers. Within the operational register set is a pointer to a location
in shared memory named the HC Communications Area (HCCA).
The operational registers contain control, status, and list pointer registers. Within the operational register set is a pointer to a location
in shared memory named the HC Communications Area (HCCA).
2.
The HCCA is the second communication channel. The HC is the master for all communication on this channel. The HCCA
contains the head pointers to the interrupt endpoint descriptor lists, the head pointer to the done queue, and status information
associated with start-of-frame processing.
contains the head pointers to the interrupt endpoint descriptor lists, the head pointer to the done queue, and status information
associated with start-of-frame processing.
Figure 12-2. Communication Channels
NOTE
The Open Host Controller Interface (OHCI) specification describes the Host Controller
Communication Area (HCCA), which is located in memory (as opposed to the USB module register).
The start address (base address) of that memory area is defined by the USB controller register HC
Communication Register.
Communication Area (HCCA), which is located in memory (as opposed to the USB module register).
The start address (base address) of that memory area is defined by the USB controller register HC
Communication Register.
Operational
Registers
Mode
Host Controller Communications Area
HCCA
Status
Event
Frame Int
Control
Interrupt 0
Interrupt 1
Interrupt 31
. . .
Interrupt 2
Done
Bulk
Ratio
Shared RAM
OpenHCI
Device Enumeration
Device Register in
Memory Space
. . .
. . .