Universal Serial Bus OHCI Host Controller User's Guide

3.11 HC Head Bulk Register (HCBULKHEADED)
3.12 HC Current Bulk Register (HCBULKCURRENTED)
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The HC head bulk register (HCBULKHEADED) defines the physical address of the head endpoint
descriptor (ED) on the bulk ED list. HCBULKHEADED is shown in Figure 12 and described in Table 12 .
Figure 12. HC Head Bulk Register (HCBULKHEADED)
31 16
BHED
R/W-0
15 4 3 0
BHED Reserved
R/W-0 R-0
LEGEND: R/W = Read/Write; R = Read only; - n = value after reset
Table 12. HC Head Bulk Register (HCBULKHEADED) Field Descriptions
Bit Field Value Description
31-4 BHED 0-FFF FFFFh Physical address of the head ED on the bulk ED list. This field represents bits 31-4 of the physical
address of the head ED on the bulk ED list. EDs are assumed to begin on a 16-byte aligned
address, so bits 3-0 of this pointer are assumed to be 0. For the restrictions on physical
addresses, see Section 2.7 .
3-0 Reserved 0 Reserved
The HC current bulk register (HCBULKCURRENTED) defines the physical address of the next endpoint
descriptor (ED) on the bulk ED list. HCBULKCURRENTED is shown in Figure 13 and described in
Table 13 .
Figure 13. HC Current Bulk Register (HCBULKCURRENTED)
31 16
BCED
R/W-0
15 4 3 0
BCED Reserved
R/W-0 R-0
LEGEND: R/W = Read/Write; R = Read only; - n = value after reset
Table 13. HC Current Bulk Register (HCBULKCURRENTED) Field Descriptions
Bit Field Value Description
31-4 BCED 0-FFF FFFFh Physical address of the current ED on the bulk ED list. This field represents bits 31-4 of the
physical address of the next ED on the bulk ED list. EDs are assumed to begin on a 16-byte
aligned address, so bits 3-0 of this pointer are assumed to be 0. For the restrictions on physical
addresses, see Section 2.7 .
A value of 0 indicates that the USB host controller has reached the end of the bulk ED list without
finding any transfers to process. This register is automatically updated by the USB host controller.
3-0 Reserved 0 Reserved
Universal Serial Bus OHCI Host Controller22 SPRUFM8 – September 2008
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