Chapter 7 |
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Wireless USB Framework |
Wireless Universal Serial Bus Specification, Revision 1.0 |
The field bmBandGroup is a bit mask that reports which UWB band groups are supported by this implementation. A 1B in a bit position indicates all of the bands and channels in the associated PHY bandgroup are supported (i.e. a 1B in bit position 0 indicates that all bands in band group one are supported). For this revision of the specification, all devices are required to support bandgroup one (0001H). At this time, only 5 bandgroups are defined, therefore bits [15:5] are reserved. For full details on the PHY, refer to reference [4].
7.4.2 Configuration
The configuration descriptor describes information about a specific device configuration. Please refer to Section 9.6.3 of the USB 2.0 specification for a full description of the Configuration descriptor. The descriptor is included in its entirety below (for completeness). The Wireless USB specific additions/requirements are documented in the description column of Table 7-30.
Table 7-30. Standard Configuration Descriptor
Offset |
Field |
Size |
Value |
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Description |
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0 |
bLength |
1 |
Number |
Refer to Table 9-10 in Section 9.6.3 in the USB 2.0 |
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specification for a full description. |
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1 |
bDescriptorType |
1 |
Constant |
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2 |
wTotalLength |
2 |
Number |
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4 |
bNumInterfaces |
1 |
Number |
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5 |
bConfigurationValue |
1 |
Number |
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6 |
iConfiguration |
1 |
Index |
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7 |
bmAttributes |
1 |
Bitmap |
Configuration characteristics |
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D7: |
Reserved (set to one) |
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D6: |
Self-powered |
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D5: |
Remote Wakeup |
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D4 |
Battery-powered |
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D3...0: Reserved (reset to zero) |
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D7 is reserved and must be set to one for historical |
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reasons. |
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All attributes are available for a USB 2.0 device |
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implementation. |
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A Wireless USB device must always set Self- |
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powered (D6) to a one (1B). |
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If a device configuration supports remote wakeup, |
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D5 is set to one. |
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8 |
bMaxPower |
1 |
mA |
A Wireless USB device must always set this field to |
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zero. |
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Chapter 7 |
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Wireless USB Framework |
Wireless Universal Serial Bus Specification, Revision 1.0 |
7.4.3 Endpoint
The purpose and function of the endpoint descriptor is the same as defined in the USB 2.0 specification, see Section 9.6.6. This section describes the requirement modifications to the endpoint descriptor required for Wireless USB. The entire descriptor from the USB 2.0 specification is repeated here for convenience, with the explicit changes for Wireless USB identified. In addition, Wireless USB defines an Endpoint Companion descriptor for endpoint capabilities required for Wireless USB, that would not fit inside the existing endpoint descriptor footprint.
A Wireless USB endpoint descriptor must not be used in a USB 2.0 (wired) device configuration.
Table 7-31. Standard Endpoint Descriptor for Wireless USB Devices
Offset |
Field |
Size |
Value |
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Description |
0 |
bLength |
1 |
Number |
Size of this descriptor in bytes |
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bDescriptorType |
1 |
Constant |
ENDPOINT Descriptor Type |
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bEndpointAddress |
1 |
Endpoint |
The address of the endpoint on the USB device |
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described by this descriptor. The address is encoded |
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as follows: |
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Bits |
Description |
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3:0 |
The endpoint number |
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6:4 |
Reserved and must be set to zero |
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7 |
Direction (ignored for Control endpoints) |
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0B |
OUT endpoint |
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1B |
IN endpoint |
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Wireless USB Framework |
Wireless Universal Serial Bus Specification, Revision 1.0 |
Table 7-31. Standard Endpoint Descriptor for Wireless USB Devices (cont.)
Offset |
Field |
Size |
Value |
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Description |
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3 |
bmAttributes |
1 |
Bitmap |
This field describes the endpoint’s attributes when it is |
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configured using the bConfigurationValue. |
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Bits |
Description |
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1:0 |
Transfer type. Values have the following |
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encoding: |
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00B |
Control |
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01B |
Isochronous |
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10B |
Bulk |
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11B |
Interrupt |
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6:2 |
This field is reserved and must be set to |
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zero if the Transfer Type field is Control |
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or Bulk. |
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If the Transfer Type field is Interrupt, |
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then bits [6:3] are reserved and must be |
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set to zero and bit [2] has the following |
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meaning: |
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0B |
Normal power interrupt |
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endpoint |
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1B |
Low power interrupt endpoint |
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If the Transfer Type field is Isochronous, |
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then this field has the following encoding: |
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Bits |
Meaning |
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3:2 |
Synchronization type |
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00B |
No Synchronization |
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01B |
Asynchronous |
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10B |
Adaptive |
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11B |
Synchronous |
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5:4 |
Usage type |
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00B |
Data endpoint |
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01B |
Feedback endpoint |
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10B |
Implicit feedback |
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endpoint |
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11B |
Reserved |
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6 |
Reserved. Must be zero. |
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7 |
Data packet size adjustment flag. This bit |
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must be set to zero for Control and |
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Isochronous endpoints. |
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0B |
Data packet size adjustment |
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not supported |
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1B |
Data packet size adjustment |
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supported |
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Chapter 7 |
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Wireless USB Framework |
Wireless Universal Serial Bus Specification, Revision 1.0 |
Table 7-31. Standard Endpoint Descriptor for Wireless USB Devices (cont.)
Offset |
Field |
Size |
Value |
Description |
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4 |
wMaxPacketSize |
2 |
Number |
When transfer type is bulk, control or interrupt: |
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Maximum packet size this endpoint is capable of |
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sending or receiving when this configuration is |
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selected. |
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If the transfer type is isochronous the value of this |
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field is the logical maximum packet size. |
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Note: If there are not software compatibility issues |
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using the wOverTheAirPacketSize, wMaxPacketSize |
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must be set to the same value as |
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wOverTheAirPacketSize. |
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Note, for all endpoints, bits [15:0] specify the |
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maximum packet size (in bytes). Note that each |
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endpoint transfer type has additional constraints |
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defined that limit the valid range of values for this |
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field. See Chapter 4 For additional details. |
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6 |
bInterval |
1 |
Number |
When the transfer type is bulk or control, this field is |
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reserved and must be set to zero. |
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For interrupt endpoints, the bInterval value is used as |
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the exponent for a 2bInterval-1 value; e.g., a bInterval of |
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6 means a period of 32 (26-1) units of 128 |
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microseconds. |
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For wireless interrupt endpoints this value must be |
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from 6 to 16. |
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Note: Not all service interval bounds in this range |
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may be achievable. See Section 4.11.2.2 for details. |
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For isochronous endpoints the value of this field is |
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the logical service interval. This field allows |
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isochronous endpoints to report a different value than |
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bOverTheAirInterval to software for legacy |
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compatibility reasons. The encoding is identical to |
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the USB 2.0 specification encoding for FS/HS |
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isochronous endpoints. The logical service interval |
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value must be in the range 1 to 16. If there is no need |
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to report different values the bInterval and |
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bOverTheAirInterval.values must be identical. |
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A continuously scalable dynamic switching capable |
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isochronous endpoint specifies zero for the bInterval |
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value and must support any interval. |
The bmAttributes field has several changes from the definition in the USB 2.0 specification. These are enumerated below:
•Bits [6:2] are interpreted based on the value of the Transfer Type field. They are reserved and must be zero if Bulk or Control.
•Bit [2] for an Interrupt type endpoint flags whether the endpoint is a normal or low-power type endpoint (see Section 4.6) but the remaining bits [6:3] are reserved and must be set to zero.
•For Isochronous, the purpose of bits [5:2] remains unchanged from USB 2.0.5 Bit [6] is reserved and must be set to zero.
5 Warning: Acceptable response timeouts for feedback endpoints may be significantly longer than wired USB 2.0.
169