TUSB3200 datasheet(20/93 Pages) TI

20 / 93 page

2–4

2.2.2

Device Initialization

After a power-on reset is applied to the TUSB3200 device, the 8052 MCU will execute a boot loader program from

the 4K byte boot ROM mapped to the program memory space. During device initialization, the boot loader program

downloads the application program code from an external EEPROM through the I2C interface. This requires that a

binary image of the application code be written to the 8K byte code RAM in the TUSB3200 device.

All memory mapped registers are initialized to a default value as defined in Appendix A,

MCU Memory and Memory-

Mapped Registers. The TUSB3200 device powersup with a default function address of zero and disconnected from

the USB.

2.2.2.1 Boot Load from EEPROM

Loading the application code from an external serial EEPROM requires a preprogrammed memory device containing

an informative header and the application code. While the application code is being downloaded, the TUSB3200 will

remain disconnected from the USB. When the code download is complete, execution of the application code should

connect the TUSB3200 to the USB. In this situation, the TUSB3200 will enumerate using the vendor ID and product

ID contained in the application code.

2.2.2.2 EEPROM Header

For both application code and USB device information stored in a EEPROM device, a common header format is used

that proceeds the data payload. Table 2-1 shows the format and information contained in the header.

Table 2–1. EEPROM Header

OFFSET

TYPE

SIZE

VALUE

Signature

0x04513200

Header size

Version

Firmware version

EEPROM type

0x01 = Reserved

0x02 = Reserved

0x03 = Reserved

0x04 = Reserved

0x05 = Reserved

0x06 = Reserved

0x07 = Reserved

0x08 = Reserved

0x09 = 24C32

0x0A =24C64

0x0B

…0xFF = Reserved

Data type

0x01 = Application code

0x02

…0xFF = Reserved

Data size

Data payload only size

Check sum

Check sum of the data payload

beginning at location Check Sum + 2

Data

Data payload

The s

ignature field is used for the detection of a EEPROM device connected to the TUSB3200. The header size field

supports future updates of the header. Data begins right after the header. The

version field identifies the header

version. The

EEPROM type field identifies the specific EEPROM device being used. The data type field describes

the nature of data stored in the EEPROM (application code or USB device information). The

data size field holds the

length of the data payload starting from the end of the header. The

check sum field contains the check sum for the

data payload portion of the EEPROM.

2.2.2.3 EEPROM Data Type

The two types of data that are stored in the EEPROM are application code and USB device information.

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