RM0319 datasheet(51/368 Pages) STMICROELECTRONICS

51 / 368 page

RM0319

BootROM

Doc ID 022640 Rev 3

51/368

5.6.7

Ethernet boot

Ethernet boot mode is supported via the MII0 interface of the SPEAR320S.

There are two different Ethernet boot modes:

●

Ethernet I2C boot mode

●

Ethernet SPI boot mode

The only difference between these two modes is the underlying protocol used to read the

MAC address from EEPROM. The modes are selected by setting the booting pins (see

Section 5.3).

●

In Ethernet I2C boot mode, the device tries to read the MAC address from the

EEPROM using the I2C protocol. The EEPROM is assumed to be present at I2C

address 0x50.

●

In Ethernet SPI boot mode, the device tries to read the MAC address from the

EEPROM using the SPI protocol. EEPROM is assumed to be on CS 0.

For both types of EEPROMs, BootROM first tries to see if it contains a valid MAC address or

not. This is determined by reading two bytes from offset 0 (in both cases). For a MAC

address to be valid, the first byte should be 0x55 and the subsequent byte should be 0xAA.

Otherwise, it considers the MAC address stored in EEPROM as valid and reads it. So, the

next 6 bytes (from offset 0x2 in the EEPROM) are considered as the MAC address and the

booting proceeds further.

Pictorially, for EEPROM to have a valid MAC address its contents should be:

Address

offset

Contents

Note:

If there is no EEPROM present on the board or the MAC address is invalid, the device uses

the default MAC address 00:80:E1:00:55:01

Additionally, Ethernet boot mode uses the following two protocols:

●

DHCP: To acquire configuration information, such as IP address, default route and

TFTP server IP address

●

TFTP: To receive X-Loader and U-Boot images

Once the device has its own IP, it can communicate with the TFTP server to download the

images and execute them. The first image which is downloaded is X-Loader. It is

responsible for initializing the PLLs and DDR memory. The U-Boot image is downloaded

and run after X-Loader has completely run.

The boot mode flow is described below. (see also Figure 14):

Once the SPEAr device gets the MAC address, it initiates the DHCP protocol and

broadcasts a DHCP DISCOVER message.

The DHCP server (in the network) must be configured to recognize the MAC address

that the device uses so that it can respond with appropriate network parameters (IP

address, default Gateway, subnet mask and TFTP SERVER IP). So, in response to

0x0

0x1

0x2

0x3

0x4

0x5

0x6

0x7

0x55

0xAA

MAC01

MAC02

MAC03

MAC04

MAC05

MAC06

RM0319 Datasheet(PDF) 51 Page - STMicroelectronics

RM0319 Datasheet(HTML) 51 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Descarga

Enlace URL