ISP1362
Single-chip USB OTG controller
Philips Semiconductors
15.3 HC Root Hub registers
All registers included in this partition are dedicated to the USB Root Hub, which is an
integral part of the HC although it is a functionally a separate entity. The HCD
emulates USB Driver (USBD) accesses to the Root Hub by using a register interface.
The HCD maintains many USB-defined hub features that are not required to be
supported in hardware. For example, the Hub’s device, Configuration, Interface and
Endpoint Descriptors are maintained only in the HCD, as well as some static fields of
the Class Descriptor. The HCD also maintains and decodes the address of the Root
Hub device and other trivial operations that are better suited to software than to
hardware.
Root Hub registers are developed to maintain the similarity of bit organization and
operation to typical hubs found in the system.
Four registers are defined as follows:
• HcRhDescriptorA
• HcRhDescriptorB
• HcRhStatus
• HcRhPortStatus[1:NDP].
Each register is read and written as a DWord. These registers are only written during
initialization to correspond with the system implementation. The HcRhDescriptorA
and HcRhDescriptorB registers should be implemented such that they are writeable,
regardless of the USB states of the HC. HcRhStatus and HcRhPortStatus must be
writeable during the USBOperational state.
15.3.1 HcRhDescriptorA register (R/W: 12H/92H)
The HcRhDescriptorA register is the first register of two describing the characteristics
of the Root Hub. The bit allocation is given in Table 55.
Code (Hex): 12 — read
Code (Hex): 92 — write
Table 55: HcRhDescriptorA register: bit description
Bit
31
30
29
28
27
26
25
24
Symbol
Reset
Access
Bit
POTPGT[7:0]
1
1
1
1
1
1
1
1
R/W
23
R/W
22
R/W
21
R/W
20
R/W
19
R/W
18
R/W
17
R/W
16
Symbol
Reset
Access
Bit
reserved
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
15
14
13
12
11
10
DT
0
9
8
Symbol
Reset
Access
reserved
NOCP
0
OCPM
1
NPS
0
PSM
1
-
-
-
-
-
-
R/W
R/W
R
R/W
R/W
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© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
Product data
Rev. 03 — 06 January 2004
82 of 150
NXP [ NXP ]
