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AppendixGUSB-MODEVMProtocol
G.1USB-MODEVMProtocol
AppendixG
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TheUSB-MODEVMisdefinedtobeaVendor-Specificclass,andisidentifiedonthePCsystemasan
NI-VISAdevice.BecausetheTAS1020hasseveralroutinesinitsROMwhicharedesignedforusewith
HID-classdevices,HID-likestructuresareused,eventhoughtheUSB-MODEVMisnotanHID-class
device.DataispassedfromthePCtotheTAS1020usingthecontrolendpoint.
DataissentinanHIDSETREPORT(seeTableG-1):
TableG-1.USBControlEndpoint
HIDSETREPORTRequest
PartValueDescription
bmRequestType0x2100100001
bRequest0x09SET_REPORT
wValue0x00don'tcare
wIndex0x03HIDinterfaceisindex3
wLengthcalculatedbyhost
DataDatapacketasdescribedbelow
Thedatapacketconsistsofthefollowingbytes,showninTableG-2:
TableG-2.DataPacketConfiguration
ByteNumberTypeDescription
0InterfaceSpecifiesserialinterfaceandoperation.ThetwovaluesarelogicallyORed.
Operation:
READ0x00
WRITE0x10
Interface:
GPIO0x08
SPI_160x04
I2C_FAST0x02
I2C_STD0x01
SPI_80x00
1I
2
CSlaveAddressSlaveaddressofI
2
CdeviceorMSBof16-bitregaddrforSPI
2LengthLengthofdatatowrite/read(numberofbytes)
3RegisteraddressAddressofregisterforI
2
Cor8-bitSPI;LSBof16-bitaddressforSPI
4..64DataUpto60databytescouldbewrittenatatime.EP0maximumlengthis64.Thereturn
packetislimitedto42bytes,soadviseonlysending32bytesatanyonetime.
Exampleusage:
Writetwobytes(AA,55)todevicestartingatregister5ofanI
2
CdevicewithaddressA0:
[0]0x11
[1]0xA0
[2]0x02
[3]0x05
[4]0xAA
[5]0x55
46USB-MODEVMProtocolSLAU261–November2008
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