TUSB3410 datasheet(76/92 Pages) TI

76 / 92 page

11–6

Table 11–5. String Descriptor (Continued)

OFFSET

FIELD

SIZE

VALUE

DESCRIPTION

‘e‘,0x00

‘v’,0x00

‘I,0x00

‘c’,0x00

‘e’,0x00

bLength

Size of string 3 descriptor in bytes

bDescriptorType

0x03

STRING descriptor type

bString

r0,0x00

UNICODE

r1,0x00

R0 to rF are BCD of SERNUM0 to

r2,0x00

SERNUM7 registers. 16 digit hex

r3,0x00

16 digit hex numbers are created from

r4,0x00

SERNUM0 to SERNUM7 registers

r5,0x00

r6,0x00

100

r7,0x00

102

r8,0x00

104

r9,0x00

106

rA,0x00

108

rB,0x00

110

rC,0x00

112

rD,0x00

114

rE,0x00

116

rF,0x00

11.4 External Device Header Format

The header can be restored in various storage devices such as ROM, parallel/serial EEPROM, I2C, or flash ROM.

A valid header should contain a product signature and one or more descriptor blocks. The descriptor block contains

the descriptor prefix and content. In the descriptor prefix, the data type, size, and checksum are specified to describe

the content. The descriptor content contains the necessary information for the bootcode to process.

The header processing routine always counts from the first descriptor block until the desired block number is reached.

The header reads in descriptor prefix with the size of 4 bytes. This prefix contains the type of block, size, and

checksum. For example, if the bootcode would like to find the position on third descriptor block, it reads in the first

descriptor prefix, calculates the position on the second descriptor prefix based on the size specified in the prefix.

bootcode, then repeats the same calculation to find out the position of the third descriptor block.

Note that the header-processing routine of the TUSB3410 only supports the I2C device. No other storage device

should be used to store header information.

11.4.1 Product Signature

The product signature should be stored at the first 2 bytes of storage device. These 2 bytes should match the product

number. The order of these 2 bytes should be the LSB first and then the MSB. For example, UMP (TUSB5152) is

0x5152. Therefore, the first byte should be 0x52 and the second byte should be 0x51.

The TUSB3410 bootcode searches the first 2 bytes of the I2C device. If the first 2 bytes are not 0x10 and 0x34, the

bootcode skips the header processing.

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