Lucent Technologies USS-720 manual USB-to- Ieee, Configuration Descriptor

Preliminary Data Sheet, Rev. 5	USS-720	Instant USB
September 1999	USB-to-IEEE	1284 Bridge

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				Endpoint Number 0			Endpoint Number 0
			8 bytes					8 bytes			8 bytes
Bulk Out Pipe			Endpoint Number 1				Endpoint Number 1			Endpoint Number 1
			64 bytes					64 bytes			64 bytes
Bulk In Pipe				—			Endpoint Number 2			Endpoint Number 2
								64 bytes			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.

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