LAN9730 Datasheet, PDF (35/222 Pages) SMSC Corporation – High-Speed Inter-Chip (HSIC) USB 2.0

LAN9730/LAN9730i
4.3.1.5 USB Command Processing
The UDC is programmed to decode USB commands. After a standard command is decoded by the UDC, it may be
passed to the CTL for completion. The CTL is responsible for implementing the Get Descriptor and vendor commands.
In order to implement the Get Descriptor command for String Descriptors, the CTL manages a 128 x 32 register file
which stores the string values for Language ID, Manufacturer ID, Product ID, Serial Number, Configuration, and Inter-
face. The RAM’s contents is initialized via the EEPROM, after a system reset occurs.
TABLE 4-3: STRING DESCRIPTOR INDEX MAPPINGS
Index
String Name
0
Language ID
1
Manufacturer ID
2
Product ID
3
Serial Number
4
Configuration String
5
Interface String
When the UDC decodes a Get Descriptor command, it will pass a pointer to the CTL. The CTL uses this pointer to deter-
mine what the command is and how to fill it.
4.3.1.6 USB Descriptors
The following subsections describe the USB descriptors.
4.3.1.6.1 Device Descriptor
The Device Descriptors are initialized based on values stored in EEPROM. Table 4-4 shows the default Device Descrip-
tor values.
TABLE 4-4: DEVICE DESCRIPTOR
Offset
Field
Size
(Bytes)
Default Value
Loaded from
EEPROM
Description
00h bLength
1
01h bDescriptorType
1
02h bcdUSB
2
04h bDeviceClass
1
05h bDeviceSubClass
1
06h bDeviceProtocol
1
07h bMaxPacketSize
1
08h IdVendor
2
0Ah IdProduct
2
0Ch bcdDevice
2
0Eh iManufacturer
1
0Fh iProduct
1
10h iSerialNumber
1
11h bNumConfigurations
1
12h
01h
0200h
FFh
00h
FFh
40h
0424h
9730h
Note 4-3
00h
00h
00h
01h
Note 4-1
Note 4-1
Note 4-2
Yes
Yes
Yes
Note 4-2
Yes
Yes
Yes
Yes
Yes
Yes
Note 4-2
Size of the descriptor in bytes
(18 bytes)
Device descriptor (0x01)
USB Specification Number which
device complies to.
Class Code
Subclass Code
Protocol Code
Maximum Packet Size for Endpoint 0
Vendor ID
Product ID
Device Release Number
Index of Manufacturer String Descriptor
Index of Product String Descriptor
Index of Serial Number String Descrip-
tor
Number of possible configurations
Note 4-1
The descriptor length and descriptor type for Device Descriptors specified in EEPROM are “don’t
cares” and are always overwritten by hardware as 0x12 and 0x01, respectively.
 2012-2015 Microchip Technology Inc.
DS00001946A-page 35