EZ-USB Datasheet, PDF (142/334 Pages) Cypress Semiconductor – The EZ-USB USB Integrated Circuit

7.3.9 Get Interface
Table 7-19. Get Interface (Actually, Get Alternate Setting AS for interface IF)
Byte
Field
0 bmRequestType
1 bRequest
2 wValueL
3 wValueH
4 wIndexL
5 wIndexH
6 wLengthL
7 wLengthH
Value
Meaning
0x81 IN, Device
0x0A “Get_Interface”
0x00
0x00
IF For this interface
0x00
1 LenL
0 LenH
8051 Response
Send AS for Interface IF over
OUT0BUF (1 byte)
The 8051 simply returns the alternate setting for the requested interface IF, and clears the
HSNAK bit by writing “1” to it.
7.3.10 Set Address
When a USB device is first plugged in, it responds to device address 0 until the host
assigns it a unique address using the Set_Address request. The EZ-USB core copies this
device address into the FNADDR (Function Address) register, and subsequently responds
only to requests to this address. This address is in effect until the USB device is
unplugged, the host issues a USB Reset, or the host powers down.
The FNADDR register can be read, but not written by the 8051. Whenever the EZ-USB
core ReNumerates™, it automatically resets the FNADDR to zero allowing the device to
come back as new.
An 8051 program does not need to know the device address, because the EZ-USB core
automatically responds only to the host-assigned FNADDR value. The EZ-USB core
makes it readable by the 8051 for debug/diagnostic purposes.
EZ-USB TRM v1.9
Chapter 7. EZ-USB CPU
Page 7-21