AN2131QC Cypress Semiconductor Corp, AN2131QC Datasheet - Page 141

• Manufacturer Part Number: AN2131QC
• Description: IC MCU 8051 8K RAM 24MHZ 80BQFP
• Manufacturer: Cypress Semiconductor Corp
• Series: EZ-USB®r

Specifications of AN2131QC

• Applications: USB Microcontroller
• Core Processor: 8051
• Program Memory Type: ROMless
• Controller Series: AN213x
• Ram Size: 8K x 8
• Interface: I²C, USB
• Number Of I /o: 24
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 80-QFP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: 428-1307

7.3.8 Set Interface
This confusingly named USB command actually sets and reads back alternate settings for
a specified interface.
USB devices can have multiple concurrent interfaces. For example a device may have an
audio system that supports different sample rates, and a graphic control panel that supports
different languages. Each interface has a collection of endpoints. Except for endpoint 0,
which each interface uses for device control, endpoints may not be shared between inter-
faces.
Interfaces may report alternate settings in their descriptors. For example, the audio inter-
face may have setting 0, 1, and 2 for 8-KHz, 22-KHz, and 44-KHz sample rates, and the
panel interface may have settings 0 and 1 for English and Spanish. The Set/Get_Interface
requests select between the various alternate settings in an interface.
The 8051 should respond to a Set_Interface request by performing the following steps:
Page 7-20
•
•
•
•
•
Perform the internal operation requested (such as adjusting a sampling rate).
Reset the data toggles for every endpoint in the interface.
For an IN endpoint, clear the busy bit for every endpoint in the interface.
For an OUT endpoint, load any value into the byte count register for every end-
point in the interface.
Clear the HSNAK bit (by writing “1” to it) to terminate the Set_Feature/Stall
CONTROL transfer.
Table 7-18. Set Interface (Actually, Set Alternate Setting AS for Interface IF)
Byte
0
1
2
3
4
5
6
7
bmRequestType
bRequest
wValueL
wValueH
wIndexL
wIndexH
wLengthL
wLengthH
Field
Value
0x0B “Set_Interface”
0x00
0x00
0x00
0x00
0x00
AS
IF
Chapter 7. EZ-USB CPU
OUT, Device
Alt Setting Number
For this interface
Meaning
Read and stash byte 2 (AS) for
Interface IF, change setting for
Interface IF in firmware
8051 Response
EZ-USB TRM v1.9