14
AT43USB324
1941A–02/01
Typical Application
The Atmel sample version of the AT43USB324 contains firmware that supports custom-
ization of the Vendor ID, Product ID, String Descriptor and the Keyboard Matrix. This
information is stored in an external AT24C02A Serial EEPROM. Data in the EEPROM is
stored in the following format.
Detailed Description
Mask Bits
The mask bits identify what features are stored in the EEPROM. A “1” in the mask bit
location means that the feature is stored and should be read. A “0”, not stored and
should not be read.
Address locations 0x04 through 0x6E store the VID, PID and String Descriptors if they
are enabled by the mask bits in location 0x03. The data are stored sequentially as
described below.
Initial Check Byte
This check byte is located immediately after the last VID, PID or strings. It is computed
as the truncated sum of Mask 1 and all the string length specified.
Address range
Content
0x00 - 0x01
EEPROM’s Signature
0x02 - 0x03
Mask Bits
0x04 Onwards
VID, PID and Strings
Initial Check Byte
0x70 - 0xFF
Keyboard Matrix
EEPROM’s Signature
Address Location
Value/Content
0x00
0x17
0x01
0x5A
Address
Location
Remark
0x02
Mask 2 - Reserved for Future Use
0x03
Mask 1
Bit 0:
VID, PID,
Version
Bit 1:
Language
String
Bit 2:
Manufacturer
String
Bit 3:
Product
String
Bit 4:
Serial
Number
String
Bit 5:
Extra Hot
Key Codes
Bit 6:
Reserved
Bit 7:
Keyboard
Matrix
VID and PID
VID
Byte 1
VID
Byte 2
PID
Byte 1
PID
Byte 2
Release #
Byte 1
Release #
Byte 2
Check
Byte
Language ID and Strings
Length (N)
Byte 1
Byte 2
Byte N - 1
Check Byte
