TUSB2046B

TUSB2046BI

SLLS413I – FEBRUARY 2000 – REVISED SEPTEMBER 2013

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Programming the EEPROM

An SGS Thompson M93C46 EEPROM, or equivalent, stores the programmable VID and PID. When the

EEPROM interface is enabled (EXTMEM = 0), the EECLK and EEDATA are internally pulled down (100

μA)

inside the TUSB2046B. The internal pulldowns are disabled when the EEPROM interface is disabled

(EXTMEM = 1).

The EEPROM is programmed with the three 16-bit locations as shown in Table 1. Connecting terminal 6 of the

EEPROM high (ORG = 1) organizes the EEPROM memory into 64×16-bit words.

Table 1. EEPROM Memory Map

ADDRESS

D15

D14

D13

D12–D8

D7–D0

00000

0

GANGED

00000

00000

00000000

00001

VID High-byte

VID Low-byte

00010

PID High-byte

PID Low-byte

XXXXXXXX

The D and Q signals of the EEPROM must be tied together using a 1-k

Ω resistor with the common I/O

operations forming a single-wire bus. After system power-on reset, the TUSB2046B performs a one-time access

read operation from the EEPROM if the EXTMEM terminal is pulled low and the chip select(s) of the EEPROM is

connected to the system power-on reset. Initially, the EEDATA terminal is driven by the TUSB2046B to send a

start bit (1) which is followed by the read instruction (10) and the starting-word address (00000). Once the read

instruction is received, the instruction and address are decoded by the EEPROM, which then sends the data to

the output shift register. At this point, the hub stops driving the EEDATA terminal and the EEPROM starts driving.

A dummy (0) bit is then output and the first three 16-bit words in the EEPROM are output with the most

significant bit (MSB) first.

The output data changes are triggered by the rising edge of the clock provided by the TUSB2046B on the

EECLK terminal. The SGS-Thompson M936C46 EEPROM is recommended because it advances to the next

memory location by automatically incrementing the address internally. Any EEPROM used must have the

automatic internal address advance function. After reading the three words of data from the EEPROM, the

TUSB2046B puts the EEPROM interface into a high-impedance condition (pulled down internally) to allow other

logic to share the EEPROM. The EEPROM read operation is summarized in Figure 10. For more details on

EEPROM operation, refer to SGS-Thompson Microelectronics M93C46 Serial Microwire Bus EEPROM data

sheet.

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