LAN9500 Datasheet, PDF (96/213 Pages) SMSC Corporation – USB 2.0 to 10/100 Ethernet Controller Promiscuous mode

LAN950x
FIGURE 5-28:
DESCRIPTOR RAM EXAMPLE
FS Configuration and Interface Descriptor
FS Device Descriptor
HS Configuration and Interface Descriptor
HS Device Descriptor
Interface String Descriptor
Configuration String Descriptor
Serial Number String Descriptor
Product Name String Descriptor
Manufacturing String Descriptor
Language ID Descriptor
= Unused Space Required For Alignment Purposes
DATAPORT
ADDR
1E
1D
1C
1B
1A
19
18
17
16
15
14
13
12
11
10
0F
0E
0D
0C
0B
0A
9
8
7
6
5
4
3
2
1
0
5.8.4 ENABLE DESCRIPTOR RAM AND FLAG ATTRIBUTE REGISTERS AS SOURCE
The EEPROM Emulation Enable (EEM) bit of the Hardware Configuration Register (HW_CFG) must be configured by
the software device driver to use the Descriptor RAM and the Attribute Registers for custom operation. Upon assertion
of EEPROM Emulation Enable (EEM), the hardware will utilize the Descriptor information contained in the Descriptor
RAM, the Attributes Registers, and the values of the items listed in Section 5.8.1 to facilitate custom operation.
5.8.5 INHIBIT RESET OF SELECT SCSR ELEMENTS
The software device driver must take care to ensure that the contents of the Descriptor RAM and SCSR register content
critical to custom operation using Descriptor RAM are preserved across reset operations other than POR. The driver
must configure the Reset Protection (RST_PROTECT) bit of the Hardware Configuration Register (HW_CFG) in order
to accomplish this.
The following registers have contents that can be preserved across all resets other than POR. Consult the register’s
description for additional details.
• Descriptor RAM
• Attribute Registers
DS00001875A-page 96
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