DS80C410 Datasheet, PDF (77/102 Pages) Dallas Semiconductor – Network Microcontrollers with Ethernet and CAN

DS80C410/DS80C411 Network Microcontrollers with Ethernet and CAN
NetBoot
The NetBoot process affords the user flexibility to download or update code remotely over the network. This
capability is quite powerful. Not only does it make firmware revisions trivial, but it also makes remote diagnostics
very practical. Also, since NetBoot can automatically reload the latest version of the user application code, the
system designer now has the option to select volatile SRAM for code storage.
For the NetBoot function to work, the DS80C410 ROM firmware must initialize certain hardware components and
create the environment needed to support the process. The NetBoot initialization code implements a primitive
memory manager, kicks off the task scheduler, and initializes the 1-Wire hardware, Ethernet driver, TCP/IP stack,
and socket layer.
Once the NetBoot initialization code has completed, the true network boot process can begin. The DS80C410
Ethernet MAC first must be assigned a physical address. Within the NetBoot process, the physical MAC address
can only be acquired through an external DS2502-(E48) 1-Wire chip. Hence, this 1-Wire chip, containing the MAC
address, is required for successful NetBoot operation. Figure 15 shows the NetBoot code flow chart.
Figure 15. NetBoot Code Flow Chart
NETBOOT
INITIALIZATION CODE
ACQUIRE MAC
ADDRESS FROM DS2502
NetBoot PROCESS
1-WIRE DEVICE
Y
WITH IP
ADDRESS
N
DHCP
GET IP ADDRESS FROM
1-WIRE DEVICE
TFTP/FLASH WRITE
FIND USER CODE
Next, the DS80C410 ROM searches the 1-Wire bus for an external device (separate from the device containing the
MAC address) that contains an IP address and TFTP server IP address. In order to correctly acquire the IP and
TFTP server addresses from an external 1-Wire device, the data read from the device must conform to a specific
format. This format is shown in Figure 16.
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