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Preliminary Data Sheet, Rev. 5 USS-720
Instant USB
September 1999 USB-to-
IEEE
1284 Bridge
Lucent Technologies Inc. 5-7
13
USB Port (continued)
Configuration Descriptor
The USS-720 has one default configuration descriptor. This descriptor has one interface, which has three alternate
settings. The three alternate settings and the endpoints that they support are shown in Table 4.
Table 4. Alternate Settings and Supported Endpoints
Endpoint Interface
Alternate Setting 0 Alternate Setting 1 Alternate Setting 2
Control Pipe Endpoint Number 0
8 bytes
Endpoint Number 0
8 bytes
Endpoint Number 0
8 bytes
Bulk Out Pipe Endpoint Number 1
64 bytes
Endpoint Number 1
64 bytes
Endpoint Number 1
64 bytes
Bulk In Pipe — Endpoint Number 2
64 bytes
Endpoint Number 2
64 bytes
Interrupt Pipe — — Endpoint Number 3
4 bytes
Table 5. Configuration Descriptor
Offset Field Size Value Description
0 bLength Byte 0x09 Size of this descriptor in bytes.
1 bDescriptorType Byte 0x02 Configuration descriptor type.
2 bTotalLength Word 0x004E Number of bytes in this configuration. This includes the configura-
tion descriptor plus all of the interface and endpoint descriptors.
4 bNumInterfaces Byte 0x01 The USS-720 has one interface.
5 bConfigurationValue Byte 0x01 Value to use as an argument to Set Configuration to select this con-
figuration.
6 iConfiguration Byte 0x00 Index of string descriptor describing this configuration.
7 bmAttributes Byte 0x80 Configuration characteristics:
Bit Description USS-720
7 Bus-powered. Set.
6 Self-powered. Cleared.
5 Remote wakeup. Cleared.
4—0 Reserved, set to 0. Cleared.
8 MaxPower Byte 0x31 Maximum power consumption of this configuration. Units are
mA
*
2; therefore, the value 0x31 is equivalent to 98 mA.