DS80C400 Maxim, DS80C400 Datasheet - Page 73

• Manufacturer Part Number: DS80C400
• Description: The DS80C400 network microcontroller offers the highest integration available in an 8051 device
• Manufacturer: Maxim

Figure 14. NetBoot Code Flow Chart
Next, the DS80C400 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 15. 1-Wire IP and TFTP Server IP Address Format
If the IP and TFTP server addresses cannot be acquired from a 1-Wire device, the NetBoot process uses DHCP to
get this information. The DS80C400 broadcasts its MAC address in a DHCP Discover packet. A DHCP server, if
available, should then respond with an IP address offering. The DS80C400 subsequently requests the IP address,
to which the DHCP server must acknowledge. In the DHCP acknowledge packet, the TFTP server IP address is
then read from the “next server IP” field. Because some DHCP servers do not allow configuration of the “next
server IP” field, the DS80C400 recognizes the site-specific option 150 (also used on Cisco IP phones to get TFTP
server IP addresses). When option 150 is present in the acknowledge packet, it will take precedence over the “next
server IP” field.
1Dh
29 (LENGTH)
54h,49h,4Eh,49h
‘TINI’
Address(4)
ADDRESS FROM DS2502
IPv4
TFTP/FLASH WRITE
INITIALIZATION CODE
Figure
FIND USER CODE
1-WIRE DEVICE
ACQUIRE MAC
NETBOOT
ADDRESS
WITH IP
DHCP
15.
Gateway(4)
IPv4
N
CONVERTED TO
PrefixLength(1)
SUBNET MASK)
73 of 97
(BYTE
Y
IPV4
TFTP Server Address(16)
NetBoot PROCESS
GET IP ADDRESS FROM
1-WIRE DEVICE
IPv4 or IPv6
1’S COMPLEMENT
OF CRC-16 (LSB
Checksum(2)
FIRST)