TNETX3100 datasheet(43/80 Pages) TI1

43 / 80 page

TNETX3100

ThunderSWITCH™ 10-PORT 10-/100-MBIT/S ETHERNET™ SWITCH

SPWS031D – JUNE 1997 – REVISED OCTOBER 1997

POST OFFICE BOX 655303

• DALLAS, TEXAS 75265

EEPROM auto-configuration from an external x24C02 EEPROM

The EEPROM can be initialized or reprogrammed through the DIO/host interface using suitable driver software.

The organization of the EEPROM data is shown in Table 7. The last register loaded is the control register. This

allows a complete initialization by downloading the contents of the EEPROM into the address-lookup table

TNETX15VEPGE. During the download, no DIO operations are permitted. The LOAD and RESET bits in the

control register cannot be set during a download, preventing a download loop.

The TNETX3100 detects the presence or absence of the EEPROM. If it is not installed, the EDIO terminal is

tied low. For EEPROM operation, the terminal requires an external pullup (see EEPROM data sheet). When

no EEPROM is detected, the TNETX3100 assumes default register values at power up and is halted.

Downloading a configuration from the EEPROM terminals is disabled when no EEPROM is present.

The first bit written to or read from the EEPROM is the most-significant bit of the byte, i.e., data bit 7. Therefore,

writing the address 0xC0 is accomplished by writing a 1, and then 1, 0, 0, 0, 0, 0, 0.

The TNETX3100 expects data to be stored in the EEPROM in a specific format. The range from 0x00 to 0x0D3

in the EEPROM is reserved for use by the adapter. The contents of the remaining bytes are undefined. The

EEPROM is read/written by a software driver through the SIO register.

A 32-bit CRC value is calculated from the EEPROM data and placed in the EEPROM in the location following

the bytes loaded into the internal register. The TNETX3100 uses this 32-bit CRC to validate the EEPROM data.

If the CRC fails, TNETX3100 registers are set to their default (hardwired) values. The TNETX3100 is then

placed in a post-reset halted state. The TNETX3100 is started through the DIO interface control register START

bit.

The EEPROM algorithm, which is the same as the algorithm for the TNETX3100 EEPROM CRC, is used by

IEEE Std 802.3 for the packet CRC calculation. EEPROM bytes are processed by the internal logic in the same

order as the bytes of a packet are processed. For a description of the algorithm, see section 3.2.8. of the IEEE

Std 802.3u specification. For reference, the equation is:

G(x) = x32 + x26 + x23 + x22 + x16 + x12 + x11 + x10 + x8 + x7 + x5 + x4 + x2 + x + 1

TNETX3100 Datasheet(PDF) 43 Page - Texas Instruments